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Bullpens: Important Factor in Race in the American League

This is not exactly talking about something that is not already known, but the bullpen on any Major League Baseball team is important. That importance might be greater now than ever, especially when talking about the American League, where just the Oakland A’s started Monday over seven games back of first place.

The big reason for the early season success of the Minnesota Twins and Houston Astros, both leading their respective divisions, has been the bullpen. With Houston, it is easier to see the numbers: the Astros have a bullpen ERA of just 2.23, which is third in baseball behind just the St. Louis Cardinals and Kansas City Royals.

With Minnesota, it is not as obvious that its bullpen has come up clutch: Their ERA is 3.72, which is 18th in baseball. However, there is another important way to evaluate a bullpen using Win Probability Added. The WPA evaluates the result of every plate appearance and assigns a value to the pitcher or hitter based upon the how the result changed the odds for each team of winning.

For instance, a base hit tying the game during the ninth innings changes the odds more than does a hit during the sixth of a game that is 10-1.

This method is as close to rating clutch as one can be as it helps to determine who is good in games that are close, and late in games that are close.

The Twins bullpen excels in that stat. Glen Perkins the stopper has not blown a save. Just like the Astros, the Twins when leading after eight innings are an incredible 27-0. However, Minnesota has lost just one game the entire season when leading starting the sixth inning or later.

Compare that with a team such as Seattle, who has a bullpen ERA of 3.73. The Mariners have lost five times when leading following the fifth inning and its bullpen is 6-13 compared to 8-6 for the Twins.

The record of wins and losses for the bullpens can be somewhat deceiving if an offense can never score during a tied game, which is the reason WPA is more of a realistic look at the overall situation.

Good bullpens are able to keep leads during close games or hold the score in a tie game to allow the offense to have a chance to win it.

As of Monday, Minnesota’s bullpen led the majors at 3.75 in Win Probability Added, while at No. 26 with -1.39 was Seattle. As of Monday, the top seven teams in WPA all were over .500.

A mediocre bullpen will not kill the chances of a playoff team, but most teams that reach the postseason have strong bullpens and this season in the American League, it should be no different. Minnesota and Houston are living proof at the moment of just that.

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