Field Dimension, Turf and Home Field Advantage in MLS

During last weekend’s podcast, we discussed home field advantage and where it might come from. There is much literature to suggest that home field advantage comes largely from rowdy home crowds—crowds that both encourage the home team to be more aggressive and encourage the referees to be more biased—but you probably already presumed that.

We went on to talk about “home specialists,” or teams that play especially well at home in a given season. An article on the site The Power of Goals theoretically explains why home specialists from any single season tend to be products of statistical noise rather than signal. That’s not to say there aren’t home specialists out there, only that it is nearly impossible to identify them statistically in a single season.

Picking out the teams that have performed markedly better at home, and then retroactively seeking explanations to match the traits of those teams is known as cherry picking, and it’s likely to lead to false conclusions (On the podcast, I recounted an example from the book Naked Statistics by Charles Wheelan as to why this can lead to trouble). Instead, identifying traits of teams and stadia first, and then checking for measurable differences in home performance based on those traits is a more sound approach.

We have mentioned around here before that Houston’s narrow home pitch might have helped the Dynamo to one of the best home records since BBVA Compass Stadium was built in preparation for the 2012 season. Indeed, Houston’s field is the narrowest in the league at 70 yards, and the Dynamo’s home goal differential is a whopping 1.33 goals better at home than on the road. However, the only reason we considered field dimensions was because Houston has performed so well at home.

We went like this:

Extreme split for Houston –> Field Dimensions must matter

But we should have thought like this:

Field Dimensions –> Extreme splits?

To advance the discussion, I gathered data going back to the 2010 season in order to look for explanatory patterns in two observable variables of stadia: field dimensions and surface. If teams are able to train on especially large or especially small fields, or on turf, such differences in the pitches may give home teams a leg up in matches played on those familiar pitches.

It turns out there is not enough evidence that either turf surfaces or field dimensions have much to do with home success.

Surface vs. Home success

There are currently four teams that play on turf: Portland, Seattle, Vancouver and New England. While the Timbers and Whitecaps have dominated at home, The Sounders and Revs have been sub par relative to the league in that department. Considering I didn’t account for the confounding variable that two of these teams play in front of some of the rowdiest fans in MLS, the “turf effect” may not even exist at all. It’s hard to say with only four teams playing on turf, three of which are not even in their adolescence as franchises.

Width vs. Home success

Field dimensions showed minimal effects, as well. Though Houston’s small, 70-by-115-yard pitch has correlated with its home success, that correlation is not true of other small stadia. The next-smallest stadium can be found in Washington D.C.,** but DCU has actually performed a little worse at home relative to the typical league splits. Montreal has the widest pitch at 77 yards, and yet, also has performed well. There is a chance that teams with extreme widths—extremely narrow or extremely wide—have some sort of advantage, but we’re going to have to wait for additional data from Houston and Montreal to be more definitive about that.

The vast majority of MLS pitches, 16-of-19 in fact, are either 74 or 75 yards wide. So even the two extremes in Houston and Montreal are not all that different. Houston could be a team built to play on a narrow pitch, but I’m skeptical that A) Soccer Analytics have come far enough for a general manager to sort that out and B) that 4-5 yards would make such a big difference.

Though I can’t say for sure that the pitch effects are non-existent, I can say pretty confidently that they aren’t pronounced or noticeable in a single season. Right now, I would argue it’s more likely that Montreal and Houston have performed so well at home due to the random variation of only two seasons of data. We will have to wait another few seasons to check on that one.

*Vancouver plays on Astroturf while the other three play on Field Turf.

**DCU’s field at RFK is a little wider at 72 yards, and actually a little shorter at 110 yards. 


PDO: Week 22 Rankings

I dropped the ball a bit last week not updating the tables. Here is how they look as of this past weekend’s results.

Team Shots Against GA Sv% SoT GF SH% TSR Points Games PPG PDO
Portland Timbers 89 20 77.53% 101 30 29.70% 0.532 34 21 1.62 1072
New England Rev. 85 19 77.65% 84 22 26.19% 0.497 30 21 1.43 1038
New York Red Bulls 92 27 70.65% 88 29 32.95% 0.489 35 22 1.59 1036
Houston Dynamo 83 20 75.90% 81 22 27.16% 0.494 30 20 1.5 1031
Salt Lake 102 24 76.47% 121 32 26.45% 0.543 37 22 1.68 1029
Dallas 109 27 75.23% 98 27 27.55% 0.473 32 21 1.52 1028
Vancouver Whitecaps 92 29 68.48% 98 32 32.65% 0.516 32 21 1.52 1011
Philadelphia Union 97 30 69.07% 102 32 31.37% 0.513 34 22 1.55 1004
Seattle Sounders FC 80 22 72.50% 76 21 27.63% 0.487 28 19 1.47 1001
Colorado Rapids 92 24 73.91% 91 23 25.27% 0.497 34 23 1.48 992
Montreal Impact 92 29 68.48% 105 31 29.52% 0.533 35 20 1.75 980
Columbus Crew 99 27 72.73% 94 23 24.47% 0.487 23 21 1.1 972
Kansas City 63 21 66.67% 103 29 28.16% 0.620 36 22 1.64 948
San Jose Earthquakes 109 33 69.72% 87 21 24.14% 0.444 27 22 1.23 939
CD Chivas USA 118 37 68.64% 69 17 24.64% 0.369 17 21 0.81 933
L.A. Galaxy 76 27 64.47% 108 30 27.78% 0.587 33 22 1.5 923
Toronto FC 77 29 62.34% 69 17 24.64% 0.473 17 21 0.81 870
Chicago Fire 85 30 64.71% 103 20 19.42% 0.548 25 20 1.25 841
DC 93 35 62.37% 62 8 12.90% 0.400 10 21 0.48 753

Again, Portland, even with their loss, retains their title as the luckiest club in MLS by PDO*. Meanwhile, New England continues to mystify as they pretty much pulled that win together with duct tape, spit and some wood glue. Is Jay Heaps really Macgyver? I’m going to guess no, though as we talked about on the podcast, home field advantage not only helps to place pressure on the ref, but it may also encourage more aggression from the home side. One can only wonder if Jay Heaps is able to simulate this effect with a stirring pep talk prior to the match against a terrible team on the road.

However, just like how Chivas and Toronto have been largely unaffected this season, likely due to some terrible play and a limited talent base, you have to wonder if we are seeing many of these clubs performing at their true rates. I don’t think you can completely attribute RSL’s finishing success to luck when defensively they have some great pieces and offensively they, again, have some great pieces.

As we watch the year unfold it’s going to be rather interesting to see where these clubs end up with playoff spots at seasons end.


*PDO here is based on shots on target, not total attempts. 

A Look At The Weekend Performances Within the Final Third

I just recently discovered that the Golazo web application—with up-to-the-minute statistical game information courtesy of—provides details for teams in the final third. Sadly enough they don’t keep the data available for long so I took advantage of a late evening to tally up the following numbers over the nine MLS matches this weekend. Below are the passing rates for each team in the final third of the pitch.

 Team Pass Completions Pass Attempts Pass Percentages Opponent
Union 68 105 74.20% Vancouver
RSL 68 98 72.40% NYRB
NYRB 89 131 69.10% RSL
San Jose 60 97 67.50% Portland
Houston 92 141 67.30% Chicago
Portland 91 146 66.40% San Jose
New England 72 121 66.20% DC
DC 69 115 64.10% New England
Sporting KC 75 121 63.50% Montreal
Colorado 64 113 63.30% LA Galaxy
LA Galaxy 69 121 63.20% Colorado
Toronto FC 85 137 62.90% Columbus
Columbus 54 107 62.50% Toronto FC
Seattle 67 117 61.50% Chivas
Chicago 57 103 61.10% Houston
Vancouver 51 102 55.30% Union
Chivas 54 108 52.00% Seattle
Montreal 31 80 50.80% Sporting KC

There really isn’t much in the way of true context at this point. Some of this is information is still about style rather than performance, but comparing the results and then applying some added data will be interesting. I wonder what, if anything, can be determined by this type of data.

I’d love to hear inputs from all you smart people.

ASA Podcast XV: The One Where We Talk About Home Field Advantage

We’re back in Episode 15, in this episode we talk about the USMNT and the Gold Cup Final (that the US has now already won), we talk a bit about Home Field Advantage and we finish up with a little game of Marry, Boff, Kill, announcer style. We must decide between Eric Wynalda, Gus Johnson and Ian Darke.

You can find us on both iTunes and Stitcher… please be kind on your ratings.

Analysis Evolved: Podcast XIV – The One Where We Talk American Value

This week we talk US National Team and look back on their group play, specifically the game against Costa Rica. We also take a look at some things that we’re glad for, and for other things…well, not so much. We also talk Jozy Altidore and American soccer players’ market values. And to conclude, we review our predictions from Real Salt Lake and FC Dallas match from last week and preview LA Galaxy at home against Vancouver. I hope you enjoy!

Making Note of Interesting MLS Moves: Brandon McDonald

We’re going to see a lot of people forever reference a term for finding something undervalued relative to what it provides. Such moves in sports are often spun off as “moneyball” type moves. I love the idea of finding undervalued assets, things that can have their production used in a manner which it benefits someone who actually needs it. The problem is most of the time when people refer to something as “moneyball” it’s mostly just butchering the term or passing off a sale for the sake of either saving face or trying to sound semi-intelligent about an acquisition. It just seems to be an overused term in sports today and it has started to defeat the principle of the idea.

And then there is this...

“The basic premise of ‘Money Ball’ is that you try to acquire undervalued assets,” general manager Garth Lagerwey said. “We’ve had a long track record of picking up pieces that other people don’t want anymore and cultivating their talents, and that’s a credit to our coaching staff and the guys in our locker room who believe in our system.”

Garth Lagerway, the current General Manager of Real Salt Lake, is explaining why he just worked out a deal with the worst team in the league for a player they just benched. The narrative delivered by the Salt Lake press is rather uninteresting and all together doesn’t matter. What is interesting, at least to me, is the outlook for an RSL team that has sought to add depth to their weakness. While being a club that has been pretty much on par with teams like the Portland Timbers and Seattle Sounders in terms of allowing shots, they’ve been outstanding preventing those opportunities from turning into goals. You could of course point to Nick Rimando, but also Josh Saunders who worked a shut out of his own against FC Dallas this past weekend.

However, no amounts of Saunders and Rimando are going to help the Lakers keep up with that rate. The only way they can be assured of limiting future goals is by limiting future attempts. Enter Brandon McDonald, formerly of the last place DC United, who was owed approximately 275K at the start of this season. He’s hardly a “money ball” type buy. But a couple points have been mentioned. Lagerway surrendered basically nothing very little (third-round pick (2014) and a conditional choice (2015), neither of which should have much, if any impact to the United and their chances at fielding a competitive team next season) in order to acquire someone who was instrumental in enabling his club to make a late second half run into the playoffs last season.

I’m sure our own DCU season ticket holder, Drew, and others can speak more to how well he’s performed this season. The standards set by Squwaka have him ranked as the #71 overall defender (among all defenders) with a performance score an even 150, though sorted purely by defensive score he ranks 57th overall with a score of 93. Turning to the other side of the analytical coin; Whoscored ranks him as the #2 best performer with a rating of 7.02 and leading the team in defensive actions and more specifically block shots.

Okay, so comparing him to his peers, he’s probably not “worthy” of being a bench guy on the last place team. But is he worth the 100+ thousand dollars that RSL will owe him this season on the rest of his contract. The answer is surprising. According to a couple of anonymous sources and general digging, it appears that Real Salt Lake may have a solid collection of allocation money saved for a rainy day and possibly used to pay down McDonald’s salary. Now, we don’t know much about allocation money, and the amounts that teams have are a well-guarded secret. But I was told that they planned on using a small amount on McDonald and now suddenly his salary isn’t so influential on the salary cap.

This is an interesting move and one that could go either way, good or bad. I’m not sure I would call this a “moneyball” move. But it’s certainly interesting and it’s something that I think you’ll see more of as teams fall away from the pack. It’s expensive to find players outside of the league, and many teams are in a state of transition (Seattle, for one) and do not necessarily have all the finances usually afforded them. Buying low or taking advantage of players that teams are ready to sell on—but can still be useful to your team—is always a smart business practice. I guess that kind of would qualify as a “undervalued asset”.

Right there, I made my own skin crawl.

PDO: Week 20 Update

Last week, we talked about PDO…a lot. We likely will continue to talk about PDO and monitor it through the season. After games played this past weekend here are the up-to-date rankings. I know that Matthias usually just updates his page on Monday, but I’m actually going to make these a post so that when I want to do a week-by-week investigation later on this off-season, it saves me time. Because it’s all about me.

Team SA GA GA% Sv% SF GF SH% TSR Points Games PPG PDO
Portland Timbers 83 18 0.22 0.78 93 30 0.32 0.528 33 19 1.74 1106
New England Rev. 75 16 0.21 0.79 72 22 0.31 0.490 24 18 1.33 1092
Real Salt Lake 87 18 0.21 0.79 112 32 0.29 0.563 37 20 1.85 1079
New York Red Bulls 83 24 0.29 0.71 79 29 0.37 0.488 31 20 1.55 1078
Seattle Sounders FC 73 20 0.27 0.73 61 21 0.34 0.455 24 17 1.41 1070
Houston Dynamo 76 19 0.25 0.75 76 22 0.29 0.500 29 19 1.53 1039
Vancouver Whitecaps 81 26 0.32 0.68 91 32 0.35 0.529 32 19 1.68 1031
FC Dallas 105 27 0.26 0.74 96 27 0.28 0.478 31 20 1.55 1024
Colorado Rapids 81 22 0.27 0.73 80 23 0.29 0.497 27 20 1.35 1016
Philadelphia Union 88 30 0.34 0.66 93 32 0.34 0.514 30 20 1.50 1003
Columbus Crew 90 23 0.26 0.74 89 23 0.26 0.497 23 19 1.21 1003
Montreal Impact 91 29 0.32 0.68 97 31 0.32 0.516 31 18 1.72 1001
Sporting Kansas City 56 19 0.34 0.66 92 29 0.32 0.622 33 20 1.65 976
L.A. Galaxy 70 24 0.34 0.66 100 30 0.30 0.588 30 20 1.50 957
San Jose Earthquakes 105 32 0.30 0.70 84 21 0.25 0.444 24 21 1.14 945
CD Chivas USA 107 35 0.33 0.67 63 17 0.27 0.371 14 19 0.74 943
Toronto FC 77 27 0.35 0.65 59 17 0.29 0.434 13 18 0.72 937
Chicago Fire 77 28 0.36 0.64 91 20 0.22 0.542 21 18 1.17 856
DC United 81 29 0.36 0.64 56 8 0.14 0.409 10 19 0.53 785

This week you see Montreal continue to sit somewhere rather neutral in the luck department. Interesting situation after reading Richard Whittall’s weekly analytic piece on the Canadian club yesterday. Even more-so when considering some of the screaming by the press and cries about replacing possibly replacing Marco Schallibaum  at the helm…in fact I kind of think it’s down right crazy. I wouldn’t considered the Impact to be a Supporter Shield contender—that’s just me—but it also doesn’t mean they won’t be. Their points-per-match total is third in MLS, and they still have one-two games in hand on the clubs ahead of them.

Speaking of the East. The New York Red Bulls continue their rise up the luck charts. Something to consider after defeating the Impact 4-0 this week and all the talk about “finally coming together”. Remember this graphic is about luck, not about talent. That is to say, be careful about high and lofty dreams, east siders. I can see the Red Bulls struggling to retain that first place position.

Another riser, this one out west, is Vancouver. They are on their way up with the recent performances of Kenny Miller, Camilo and Brad Knighton. Their 1.68 points-per-game average have them quietly (or, of late, not so quietly) contending for a top-3 playoff position ahead of Dallas, LA and Seattle. Something to take note and see whether they are truly overachieving and just on a hot-streak, or finally hitting a much-needed groove.

Lastly, on the subject of FC Dallas, I think it’s interesting how they’ve held pretty firm with a PDO over 1000. Expect them to continue to regress over the next few weeks. The number of shots that they are allowing to reach Raul Fernandez is quiet surprising, and the fact that they are producing an above average save% makes me question how much longer they’ll stick around. Though, admittedly, much of that has been due to George John being MIA. His return from the hamstring strain will be crucial to stopping attacks before they get to the keeper.

ASA Podcast XII: The one where we talk PDO

I hope you all have enjoyed the build up to this week’s podcast concerning PDO. In today’s episode we review the Gold Cup situation with the Mens National Team, talk a bit about PDO, and then preview Real Salt Lake and Dallas FC (so that you can see how grossly wrong we were). Enjoy!

PDO: Major League Soccer Table 7/12/13

We had a light introduction of the statistic of PDO last evening, and as promised, here is the corresponding table as it exists for Major League Soccer.

Team Games PPG TSR PDO
New England Rev. 17 1.41 0.497 1101
Portland Timbers 18 1.67 0.530 1100
Seattle Sounders FC 16 1.50 0.469 1071
FC Dallas 19 1.63 0.474 1060
Real Salt Lake 19 1.79 0.569 1049
Montreal Impact 17 1.82 0.522 1039
New York Red Bulls 19 1.47 0.480 1039
Houston Dynamo 18 1.44 0.493 1034
Vancouver Whitecaps 18 1.61 0.525 1016
Colorado Rapids 20 1.35 0.497 1016
Columbus Crew 19 1.21 0.489 1012
Philadelphia Union 19 1.42 0.520 975
L.A. Galaxy 19 1.58 0.594 967
Sporting Kansas City 19 1.58 0.603 965
San Jose Earthquakes 20 1.05 0.432 945
Toronto FC 17 0.76 0.460 940
CD Chivas USA 18 0.78 0.384 937
Chicago Fire 17 1.24 0.551 864
DC United 19 0.53 0.382 802

If you’re trying to figure out what to look at, there are a couple of things that may, possibly, jump out at you. The first being the New England Revolution sandwiched between the two best teams in MLS, Portland and Montreal. Admittedly, the club has been on a sort of hot streak but it a large percentage of their PDO comes from the lack of goals they’ve conceded. Opposing clubs have the worst conversion rate of Goals/Shots against New England.

Similarly, you see Sporting Kansas City sitting 15th in PDO and can’t help but be a little bit scared of what could come in the second half should there be positive regression. Considering all the head scratching that the media and supporters have concerning Seattle’s early exploits, Sporting has gone largely unnoticed with an underwhelming start. Yet, the TSR (explanation linked–we’ll get into this more down the road) is very much there and so are the points. An interesting out come for a club that (deservedly) had the hype machine cranked to full.

Oh, and DC United is definitely still a combination bad and unlucky. Sorry, Drew.

A little information on: PDO

With the holiday behind us we can once again start to return to the business at hand. The half-way mark is upon us and MLS has given us an exciting and very tight race across both the Western and Eastern conferences.

With that comes another week of podcasts. #AnalysisEvolved. This week we plan on talking a bit about a statistic by the name PDO. Unlike how you might imagine most statistic names coming about, or things with three random letters, this is not an acronym. It’s pronounced how it’s sounds.

Originally a hockey metric, PDO is simply the sum of save percentage and scoring percentage, then multiplied times 1000. The rest of the history as it applies to soccer isn’t necessarily important.

A great introduction to the idea and how it applies to the sport is given by Tyler Dellow of, and there is another introduction on the site Pension Plan Puppet by one “Skinny Fish.”

Both sites give examples of how PDO can potentially isolate a team’s performance over the course of a season and compare those to past performances, various incarnations of the team, and of course, other teams.

I can’t directly attribute who was the first to apply the team analysis to the sport of soccer(Grayson confirmed he was the first…). But the oldest article I can find referencing its usage within the sport comes from the ever-smart and sophisticated Canuck, James Grayson. His series of introductions to the metric is linked below.

A Premier: PDO

PDO – part I

PDO – part II

Along with an explanation of the stat and some information about how it regresses to the mean—because it’s fantastic at doing that—there is also a bit of information about how it can be used to compare different clubs to one another.

Basically, it comes down to being one of the best methods to determine the barometer of a team. While we can look at point totals and standings in the table, PDO can reasonably tell us if a team is over performing or under performing.

I’m not in any way an expert on this stat. There are of course some occasions were you may run into issues with trying to apply it to a specific scenario, and I could point anyone in search of more answers on the subject in better directions than toward myself. I could easily name about a dozen or so people that are much more versed in this metric than I am.

However, since we were going to take about it on our podcast this weekend, I wanted to give the reader/listener an opportunity to find some quick and easy references to the material before hearing us talk about it this weekend.

I’ll have an updated PDO standings for you all tomorrow which will lead into our discussions on Saturday.