Will Middlebrooks left Tuesday night's Red Sox game in Kansas City with a hamstring injury.
Middlebrooks slowed up heading from second to third base, and it was confirmed that he injured his left hamstring, according to NESN Red Sox writer Didier Morais.
Middlebrooks, who sat out Saturday's game against Baltimore, was dealing with some cramps and hamstring tightness late last week and appeared to aggravate the injury.
Nick Punto came into the game to replace the hot-hitting Middlebrooks at third base.
Since being called up to the major leagues last week, Middlebrooks has been red hot, hitting .381 with three home runs and nine RBIs.
The injury could pose a major concern for manager Bobby Valentine as Kevin Youkilis, the usual everyday third baseman, is still on the disabled list with back tightness.
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