Atletico Madrid striker, Diego Costa, could miss the first leg of their Europa League semi-final fixture against Arsenal because of an injury to his left hamstring.
The LaLiga club say the injury was diagnosed after exams on Friday.
Costa was taken off in the second leg of the Europa League quarter-finals at Sporting Lisbon on Thursday, when Atletico advanced 2-1 on aggregate.
Atletico did not state how long Costa is expected to be out for, but local media report it would take about two weeks for him to return to action.
This makes the Spain international doubtful for the first leg against Arsenal in London on April 26.
The return match is May 3 in Madrid.