In analyzing MLS shot data, I have learned that—with small sample sizes—how a team plays when the game is tied is a strong indication of how well it will do in future games. The US Mens National Team spent just four-and-a-half minutes tied Monday evening, the epitome of small sample sizes. In case you were curious, the US generated two shots during that time worth about 0.13 goals. Ghana did not generate a shot over those 4.5 minutes.
The next most-important gamestate for a team is being ahead. With at least 17 games of data in MLS, knowing how well a team did when it was leading becomes an important piece of information for predicting that team’s future success. Almost 95 minutes were spent with the US in the lead, a time in which the USMNT took six shots worth 0.5 goals to Ghana’s 21 shots worth 1.7 goals.
Though MLS is definitely far below the level of even a USA-versus-Ghana match, I think a lot of the statistics from our MLS database still apply. I wrote a few weeks back about how away teams that were satisfied with the current gamestate went overboard with their conservative play. I think that could apply to the World Cup, as well. By most statistical accounts, USA versus Ghana was a fairly even matchup going in, yet the US played an annoying conservative style after going up a goal early. It gave up a majority of possession to Ghana in the attacking third, completing just 81 passes to Ghana’s 171 in that zone—not to mention the US being tripled up in Expected Goals when it was ahead.
Granted, Expected Goals likely overestimates the losing team’s chances of scoring. But not by much. In even gamestates in MLS, we see that teams are expected to score 1.29 goals per game, and they actually score 1.30 goals per game. Virtually no difference. However, when teams are ahead they are expected to score 1.79 goals per game, yet they only score about 1.60—an 11-percent drop. This discrepancy is likely due in large part to defenses being more packed in and capable of blocking shots. Indeed, teams that are losing have their shots blocked 27 percent of the time, while teams that are winning only have their shots blocked 22 percent of the time.
All that was simply to say that Ghana’s 1.7 Expected Goals are still representative of a team that was in control—too much control for my comfort level. Even if we assume it was really about 1.5 Expected Goals against a defensive-minded American side, that still triples the USA’s shot potential. Either the US strategy was overly conservative, or Ghana is really that much better. I’d like to believe in the former, but it’s picking between the lesser of two evils.
It just doesn’t make sense to me to play conservatively to maintain the status quo. It invariably leads to massive discrepancies in Expected Goals, and too often allows the opposition an easier way to come back.