The 2009 Tigers barely outscored their opponents 745 to 743. You would expect a team with such a small run differential to finish with 81 wins, but the Tigers managed to win 86 games. The reason was because they had a record of 52-33 in games decided by just one or two runs. At the time, I theorized that they won so many close games, in part, because of Fernando Rodney’s high save conversion rate (37 for 38), seven walk-off wins and some luck.
This year, the Tigers had remarkably similar runs scored and runs allowed totals to 2009. They outscored their opponents 751 to 743, but won just 81 games. Pete Palmer – author of The Hidden Game of Baseball – estimated that a differential of ten runs is worth approximately one win. In other words, adding ten runs to a team’s season total increases their expected wins (EW) by one and subtracting ten runs decreases their expected wins by one. Palmer developed the following formula for expected wins based on that principle:
EW = games/2 + run differential/10
According to this formula, you would expect the Tigers to have 82 wins. The results for other American League teams are shown in Table 1 below. You can see that every team in the league finished within 4 wins of their expected wins. So, the formula fit reality amazingly well in the American League this year. This means that winning was largely a function of the obvious – scoring more runs and allowing fewer runs.
The results for the National League are shown in Table2. The Houston Astros were the only team falling more than five wins from their expected wins. They won seven more games than expected (76 versus 69). The reason was because they lost a lot of blow outs. They were 1-13 in games with margins of eight runs or more. The Cardinals won five fewer games than expected (86 versus 91). In their case, they were 24-7 in games decided by six or more runs.
Table 2: Wins and Expected Wins in NL in 2010
Getting back to the Tigers, why did they win five fewer games this year when their run differential was six runs more than it was in 2009? The reason was because they had less success in close games. After finishing 19 games above .500 in games decided by one or two runs last year, they were 33-38 this year.
It’s hard to blame their bullpen which was better than last’s year’s crew according to most statistics including ERA, FIP and WPA. They also had their share of dramatic victories early in the season. Some might attribute the difference in close game performance to poor managing or less desire to win, but I’m going guess that it was just a random thing.
Data for this article were abstracted from FanGraphs.com.