Team spokesman John Blake said Feldman would be re-evaluated on Monday once the Rangers return to Arlington after a seven-game road trip. Dr. Keith Meister will perform an MRI exam to determine the severity of Feldman's injury.
Feldman had entered the game with two outs in the sixth inning in relief of Texas starter Cliff Lee. He allowed a run-scoring infield single to Julio Lugo and got Nick Markakis to line out to shortstop to end the inning. He hurt himself warming up before the seventh and was replaced by lefty Mike Kirkman, who struck out the side in his Major League debut.
Feldman didn't have trouble moving around in the clubhouse after the game, explaining that the knee only gives him trouble when he pushes off in his delivery. He said he's had some soreness for a couple of days but that the knee started to buckle on him when he was warming up before the seventh inning.
"It doesn't bother me to walk or anything, except when I push off," he said.
Manager Ron Washington said the Rangers could "possibly" make a roster move on Feldman before Sunday's finale of a four-game series at Camden Yards against the Orioles, but added that it was "possible" that a decision would be held off until after the team returns home.