In Baseball-Reference box scores, you can find a goofy little stat called "wWE," which means "Winner's Win Expentancy." Quite simply, in their words:
The current probability (after the play) of the eventual winner winning at this point in the game.
wWE is a Win Probability Added stat, which is a group of stats that attempt to analyze the progression of probability of winning throughout a game, allowing us to judge the value of certain plays. Again, in their words:
These statistics generally look at the game context at the start and the end of the play and compare the batting team's probability of winning the game in both situations.
For example, in the top of the eighth, the visiting team might be down five with one out and runners on first and second. The batter then hits a home run to bring the visiting team to within two runs, still with one out, but now with no runners on base. Prior to the home run, the batting team had about a 3% chance of winning which improved to 10% following the home run. This change of 7% is credited to the batter and debited to the pitcher. Compute these for every play and every game from 1956 on and you have win probability added stats.
This stat does something that a lot of people criticize many advanced stats for not doing. It considers the context of the game. A home run with the score tied is worth much, much more than a home run with a ten-run lead. In fact, a walk or run scoring ground out in a tie game is worth more than a home run in a blowout.
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Now, looking through game logs, we have a very valuable reference for judging plays: we can judge the value of crucial plays throughout the season; which clutch plays were most clutch; which winning plays were least expected, most crucial, etc.
My survey in the coming week is more mundane and simple: Working through box scores, I am looking at each Brewers win, and evaluating the point at which the Brewers kept the lead for good -- sometimes a game-winning hit can occur in the first inning, other times a game-winning hit can occur in the 12 inning. The beauty of wWE is that we can capture the value of game-winning hits across the spectrum of game situations.
Obviously, plays the end the game immediately -- walk-off hits -- will usually be more valuable because they end the game immediately, making it impossible for the other team to come back. But inbetween the 1st and extra innings, we can find a lot of unique plays.
Here are the Brewers' April victories, and the Probability shift of the winning plays:
April 19, 2008 (@Cin): Bill Hall (T10); double +45%
April 23, 2008 (vs. PHI): Prince Fielder (B8); home run +39%
April 17, 2008 (@ StL): Prince Fielder (T10); home run +35%
April 22, 2008 (vs. STL): Gabe Kapler (B12); single +30%
April 26, 2008: (vs. FLA) Prince Fielder (B8); home run +26%
April 8, 2008 (vs. CIN): Rickie Weeks (B10); single +18%
April 13, 2008 (@ NYM): Rickie Weeks (T6); home run +17%
April 12, 2008 (@ NYM): Rickie Weeks (T5); home run +15%
April 29, 2008 (@ ChC): Bill Hall (T5); single +14%
March 31, 2008 (@ ChC): Tony Gwynn (T10); sacrifice fly +13%
April 2, 2008 (@ ChC): Rickie Weeks (T1); home run +12%
April 5, 2008 (vs. SF): Mike Rivera (B2); single +10%
April 4, 2008 (vs. SF): Prince Fielder (B1); single +8%
April 6, 2008 (vs. SF): J.J. Hardy (B2); double +7%
April 18, 2008 (@ Cin): Prince Fielder (T1); sacrifice fly -1%
Series Victories
@ Cin (April 18-19): +44% (22% shift per win)
@ NYM (April 12-13): +32% (16% shift per win)
@ ChC (March 31, April 2): +25% (12.5% shift per win)
Vs. SF (April 4-6): +25% (8.3% shift per win)
Single Victories (lost series / two game series)
Vs. PHI (April 23): +45%
@ STL (April 17): +35%
Vs. STL (April 22): +30%
Vs. FLA (April 26): +26%
Vs. CIN (April 8): +18%
@ ChC (April 29): +14%
The Brewers' series at New York in April of 2008 probably featured the most consistently crucial winning plays, right in the middle of very close ballgames. Both were Rickie Weeks home runs, one in the 5th, the other in the 6th, both providing the Brewers' the lead for good. Less than a week later, the series at Cincinnati featured the month's most-clutch, most crucial hit, a Bill Hall double in the top of the 10th (worth a 45% shift in winning probability).
One of the features of the Brewers' first half -- prior to acquiring Sabathia -- is playing above their expected win/loss record; the Brewers played roughly 4 wins above their Pythagorean and Expected W-L records, based on runs allowed and runs scored, before acquiring Sabathia in mid-July, and I think we can see why in April: although the Brewers had a few series in which they only won a single game, five of those single-game victories were above the median probability shift (the median was 15%).
In these single-victories, the Brewers stole away some very, very close games, winning in late game situations and extra innings situations; it is my hypothesis that these trends of stealing away close-game victories -- even in the midst of losing the overall series -- helped to shift the Brewers' W-L. (It also helps that the Crew won most of their blown saves in April).
Of course, April also featured some mundane victories -- including the entire sweep of the Giants at Miller Park, where the average probability shift on winning plays was under 9%. This means that the Brewers won those games early, never to relinquish the lead; those games truly were never in question.The other mundane victories occurred at Chicago to open the series, where the Tony Gwynn sacrifice fly and Rickie Weeks' game-opening home run served as rather low leverage winning plays.
Outside of the two opening series (one at home, one on the road), the Brewers had a rather hectic April, winning games in close situations, and especially late situations.
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Citation
Baseball-Reference. "Win Probability Added (WPA) Stats." Win Probability Added Glossary. October 28, 2008. Accessed February 28, 2009.