Giants first baseman Aubrey Huff bruised his right knee trying to jump over the dugout railing and join the postgame celebration of Matt Cain's perfect game.
San Francisco manager Bruce Bochy said Huff underwent an MRI early Thursday and the team is awaiting the results.
Cain threw the first perfect game in Giants history in a 10-0 win over the Houston Astros on Wednesday night - the second perfect game and fifth no-hitter in the majors this season.
Huff, a top candidate for designated hitter when the Giants visit Seattle for an interleague series this weekend, landed on his knee as he jumped over the railing and had to be helped off the field.
Huff is hitting only .120 in 19 games since being activated from the disabled list.