"I had a little issue with a hammy four or five years ago, but I really don't have any theory on what's happening now," said the 34-year-old Blake.
"I don't know if the right hamstring got overworked because the left was sore. I don't know. I need to get them stronger somehow. I'm not big for stretching, but maybe my warmup routine needs to change."
Blake is hitting .400 with 18 RBIs and 13 runs in the 19 games since Manny Ramirez was suspended. Blake leads the club with nine homers, although he hasn't had one in the past nine games. After batting eighth most of the season, he was moved into the middle of the batting order last Sunday.
Blake missed the final game of the last trip in Florida on May 17 and the first game of the last homestand on May 18 to rest the left hamstring. He said missing Saturday's game was more precautionary, but neither he nor manager Joe Torre could say whether he'd return to the lineup for Sunday night's series finale.
Blake said he was injured in the fourth inning of Friday's game. The Cubs had the bases loaded with two outs when No. 8 hitter Andres Blanco hit a slow tapper by the mound. Blake charged, reached down for the ball and said he made an "unnatural movement for me," twisting his body to align for a straight throw to first base that ended the threat.
Blake remained in to finish the game, walking to lead off the seventh inning and getting doubled off first base on Andre Ethier's double-play liner and flying out to right field for the second out in the ninth inning.
Torre said he would have pinch-run for Blake had he reached base in the ninth. Blake took batting practice and some light fielding before Saturday's game.
Mark Loretta started at third base Saturday in place of Blake.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.