Tim Howard was removed from the United States' 2-1 CONCACAF World Cup qualifying loss with Mexico on Friday after suffering an injury to his right leg in the first half.
The veteran U.S. keeper is now unlikely to make the trip to Costa Rica for the U.S.'s second Hexagonal qualifier on Tuesday, according to manager Jurgen Klinsmann.
"He pulled his muscle," Klinsmann confirmed after the match. "I think he's not able to come with us to Costa Rica, He'll have an MRI tomorrow morning. He's so experienced I think he knows it's not looking that good."
Howard got the starting nod over Middlesbrough keeper Brad Guzan for the match with El Tri in Columbus, Ohio, and immediately repaid Klinsmann's faith with a fine save of a Jesus "Tecatito" Corona curling shot early on.
However, the Colorado Rapids' No. 1 went to ground after taking a goal kick just after the half-hour mark and received attention from the U.S. medical staff for a few minutes.
Howard stayed in the match, but signaled to the bench on 40 minutes after feeling the effects of the injury following a routine save.
Guzan then came on in his place and was in goal when Rafa Marquez scored a late winner for Mexico, with the game level from earlier Miguel Layun and Bobby Wood goals.