Last week, we looked at the plethora of MLS playoff formats. Despite these changes, one durable playoff aspect is an aggregate round. MLS introduced an aggregate conference semifinal round in 2003 that remains today, and the conference finals followed suit in 2012.
I analyzed the results of the aggregate stages for the past 13 years of MLS playoffs – this equates to 120 games. The key finding is that home teams have a better record in these games than higher seeds.
For this analysis, I counted the result after 90 minutes, or 120 minutes for extra time. This means a penalty shootout win is not included if that team tied or lost the second leg. This happens infrequently, though, with the most recent example the Columbus-Colorado conference semis in 2010.
In the aggregate stages, home teams won 65 of the 120 games, or 54%. The home team also tied another 23% of the games. In comparison, the higher-seeded team won 53 games, or just 44%.
This year’s playoffs exemplified this dynamic. New York, with its 1-0 win at DC, was the only higher seed to gain three points on the road. MLS Cup finalist Portland went one better: its 2-0 win at Vancouver was the only victory away from home. The other 10 games featured a win or draw for the home team.
Framed another way, the higher-seeded team found itself disadvantaged after the first leg in four of the six series. What’s more, with away goals in place, the home team must manage the result and the score in the second leg.
It’s unclear why the aggregate format exists in the playoffs. There is a desire for all playoff teams to have a home game, but it comes at the expense of a stronger home field advantage for better teams in the regular season. It’s also incongruous with the requirements to make the playoffs. If MLS’ intent is that any team that makes the playoffs should have a good chance to win MLS Cup, then scrap the knockout round and have fewer teams qualify. If the intent is to reward regular season performance (and given Nelson Rodriguez’s quote in 2011, I think this is the case), two rounds of an aggregate series works against that goal.
Update: Replaced labels on pie charts to reflect percentages instead of games.