In a reversal of form, Red Sox slugger David Ortiz (right), widely regarded as the king of clutch, has faltered in key situations this year, while the Yankees' Alex Rodriguez, who has had a reputation for not delivering in pressure at bats, is making progress in erasing that image.
For its book Baseball Between the Numbers, Baseball Prospectus developed a method to evaluate a player's performance in the clutch and how it translates into victories for his team by comparing two statistics derived from complex formulas: expected output based on a player's overall batting performance to date that season (Wins Above Average, or WAA), and actual output based on a detailed rendering of the play-by-play data that season (Win Expectancy, or WX). The BP model shows, for example, that a team trailing by three runs with two outs and the bases loaded in the bottom of the ninth will win the game about 10% of the time; thus a player on the trailing team who hits a grand slam will be credited with .9 of a win for his club, or +.9 WX. Players that concentrate their output in such key situations can be considered clutch.
In 2006, Ortiz produced a WAA of 4.82 and a WX of 8.23 (highest in the American League). That works out to a clutch rating of +3.41 wins, meaning Ortiz produced three to four wins for the Red Sox based solely on his clutch performance. A-Rod, conversely, had a WAA of 2.21 and a WX of 1.39, for a clutch rating of -0.82 wins.
However, in games played through July 19, Rodriguez had a clutch rating of +1.46 wins this season based on his 2.94 WAA and 4.40 WX (best in the majors), while Ortiz, who was hitting only .238 in close-and-late situations, was at -0.90 (2.43 WAA, 1.53 WX).