Buchholz had attempted to field Howie Kendrick's hard grounder to the box an inning earlier, had the ball bounce behind him and when he left after the sixth he was seen on TV looking at his left hand with a trainer.
It was quite a fielding night for the Red Sox ace.
He also rolled over on his side and made a tag after bobbling Alberto Callaspo's high-chop grounder near first before making a tag in the fourth.
With two outs in the seventh, manager John Farrell and a trainer came to the mound. After a brief discussion, Buchholz walked off and was replaced by Craig Breslow.