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If the Season Ended Yesterday: BoSox, Phils Neck-and-Neck


The Boston Red Sox have dethroned the Yankees in the AL East (at least for now), driving most of the changes in the playoff probability numbers. Boston's best are now in a dead heat with the Phillies as the favorites for the World Series, both coming in at 3:1. The Yankees dropped into the 3-spot as a result of their recent skid. So says our Log5 postseason simulator based on numbers from Baseball Prospectus.*

There's a lot more to this story than likely World Series winners, however. Keep reading for the rest of it.

*We've tweaked our system since last week, fixing an error in the home field advantage calculation. See methodology below the jump.

Probability of Postseason Series Victory 8/29/2011
Inputs Outputs
Team Seed Talent LDS% LCS% WS% WS HFA
BOS 1 0.647 69.4% 39.0% 24.9% -0.9%
TEX 2 0.599 42.4% 19.1% 10.2% -0.7%
DET 3 0.551 30.6% 10.4% 4.5% -0.2%
NYY WC 0.645 57.6% 31.5% 19.9% -0.8%
PHI 1 0.619 73.4% 49.1% 24.2% 1.6%
MIL 2 0.551 53.2% 22.2% 7.7% 0.5%
ARI 3 0.495 26.6% 10.3% 2.5% 0.2%
ATL WC 0.542 46.8% 18.4% 6.2% 0.3%
AL 59.5% -2.6%
NL 40.5% 2.6%

Figures of note:

  • As of yesterday, the AL East winner was ~12% more likely to win the ALDS, ~7% more likely to win the ALCS, and ~5% more likely to win the World Series than the AL Wild Card. Think about that as the Yankees head into Beantown this week.
  • The Rangers are 4:1 to successfully defend their American League title, 9:1 to win it all for the first time.
  • If the Angels reach the playoffs as the 3-seed, we put them at 24:1 to win the World Series.
  • It'll be up to Ian Kennedy and Justin Upton to ensure the Phillies--73.4% favorites--don't make quick work of Arizona in the NLDS.
  • Having fixed an error in the home field advantage calculation, the Diamondbacks are now a distant 39:1 shot to win it all.
  • Without the D'Backs in the way, the Giants would be a distant 46:1 to repeat as World Series champs.
  • Despite the NL's World Series home field advantage, AL is still likely to produce the World Series winner considering the talent distribution across the current postseason favorites.
  • The Braves are 4:1 to return to the World Series for the first time since 1999.

Methodology: Our simulator predicts the outcome of every possible single-game match-up in every potential five- and seven-game series match-up between the eight teams currently in line for a playoff berth. Baseball Prospectus' Adjusted Hit List serves as proxy for true talent. We use the Log5 method to predict single-game match-ups, adjusting each number to reflect a 0.540 home field advantage (based on Matt Swartz's findings). The simulator does not adjust for roster discrepancies, pitching rotations, or any stadium-specific home field advantages that may or may not exist.