What Best Predicts a First Round MLS Playoff Winner?

Can you name one thing that all four MLS playoff quarterfinal winners had in common this past season? They all played fewer games than the teams that they defeated: SJ 31 vs 34 NY COL 32 vs 42 CLB LA 34 vs 42 SEA DAL 31 vs 38 RSL Once again, the curse of the CONCACAF Champions League comes into play. Only one MLS team which has made the group stage has won a playoff series (Houston 2009) in six tries. This year, Columbus, Real Salt Lake, and Seattle all are now included in that 1-5 record. I want to talk a bit more about what are the best predictors of a team advancing. I looked at all 32 quarterfinal matchups since the current two-leg aggregate format has been in place (2003), and I compared each team in a variety of statistics. It turns out that the best predictor of the ones I looked at is actually fewer games played, just beating out goal difference. Won Lost Even PCT 18 7 7 0.672 fewer games 21 11 0.656 goal difference 19 12 1 0.609 less experienced coach 19 13 0.594 momentum 19 13 0.594 higher seed 17 11 4 0.594 top goalscorer 18 13 1 0.578 goals for 18 14 0.563 home record 18 14 0.563 older team 17 15 0.531 away record 17 15 0.531 younger coach 12 10 10 0.531 won season series 16 13 3 0.547 goals against 16 16 0.500 2 year record 14 18 0.438 3 year record 13 19 0.406 coach has better all time record All records used were regular season only, and teams who didn't have a 2 or 3 year record, I used the years they had. For results from 1996-9 (such as with the coach records), shootouts were counted as draws. PPG was used for all comparisons. Momentum was a comparison of the final 5 regular season games. For this table, each "even" listing is counted like it's usually done in sports: half a win and half a loss. If you have any other ideas to look at, please comment below.