Atletico Madrid have confirmed striker Diego Costa suffered a hamstring injury in Thursday's Europa League clash with Sporting CP.
The Spain international was withdrawn in the second half of the 1-0 quarter-final second-leg loss to the Portuguese side in Lisbon and was sent for further tests.
"After undergoing medical exams this Friday, April 13, he has been diagnosed with a hamstring injury to his left leg," Atleti confirmed in a statement via their official website.
The club were unwilling to put an estimated time frame on the former Chelsea forward's recovery.
It is expected Costa will at least miss Sunday's LaLiga clash with Levante, while he is also likely to be a doubt for the following two games against Real Sociedad and Real Betis.
Atleti will hope to have the 29-year-old available for the first leg of their Europa League semi-final tie against Arsenal at the Emirates Stadium on April 26.