Jaffe: Do September streaks correlate to playoff success or failure?

From SABR member Jay Jaffe at Sports Illustrated on September 19, 2017:

Thus far in September, streaks have dominated the baseball news, namely the Indians’ record-tying 21 consecutive wins and the Dodgers’ 11 straight losses, with the Diamondbacks’ franchise record 13-game winning streak not to be overlooked. All three teams are on track for the postseason, leading to plenty of speculation as to what the past few weeks will mean for their October fates.

However, according to a 2009 study I did at Baseball Prospectus that has been frequently cited—including, coincidentally, during ESPN’s Giants-Dodgers telecast this week just as I was putting this updated version together—there is virtually no correlation between the performance of wild-card era playoff teams in September and October. 

That study examined 112 playoff-bound teams from 1995 to 2008 and how each performed in their final seven, 14 and 21 regular season games as well as those from Aug. 31 to the end of the season, which sometimes trickles into the first week of October (for the rest of this piece, I’ll refer to this as September records or September winning percentage despite the spillover). At each of those levels, what I found was an essentially random relationship between the winning percentages in those fragments and the results of the Division Series.

Read the full article here: https://www.si.com/mlb/2017/09/14/cleveland-indians-los-angeles-dodgers-playoff-odds

Originally published: September 20, 2017. Last Updated: September 20, 2017.