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WHIP stands for Walks and Hits per Inning Pitched. It’s a simple measure of a pitcher’s ability to limit baserunners, arguably the primary immediate goal of a hurler from inning to inning.

As the name implies, WHIP is calculated as follows:

WHIP = Total Walks Allowed + Total Hits Allowed / Innings Pitched

Sportswriter Daniel Okrent generally is credited with inventing WHIP, in 1979, as a better measure of pitcher effectiveness than ERA (Earned Run Average), which is influenced more heavily by overall team performance.

Okrent also came up with Rotisserie League Baseball, an early version of fantasy baseball. Hoping to make his new statistic accessible to participants in Rotisserie and fans in general, Okrent left out hit batters from his base-runner numerator because that data was not usually available in daily newspapers.

A WHIP near 1 is considered outstanding, as it means a pitcher allows around a batter per inning to reach base.

The all-time WHIP leader is Addie Joss, at 0.9678, while the modern record belongs to Mariano Rivera, at 1.0003. Clayton Kershaw is tops among modern starting pitchers at 1.0030.

Pedro Martinez holds the all-time single-season WHIP mark, at 0.7373. He accomplished that feat for the Boston Red Sox in 2000, when he allowed 32 walks and 128 hits in 217 innings pitched.

The major shortcoming of WHIP, besides the exclusion of hit batsmen, is that it neglects to account for the types of hits the pitcher surrenders. For instance, consider the two pitchers below:

Pitcher A: 100 innings pitched, 10 walks allowed, 90 hits allowed (60 singles, 20 doubles, 10 triples, 10 home runs)

Pitcher B: 100 innings pitched, 10 walks allowed, 90 hits allowed (50 singles, 20 doubles, 10 triples, 20 home runs)

Both pitchers have a WHIP of 1.0, but Pitcher A has given up only 170 total bases, while Pitcher B has allowed 200 total bases.

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