Villarreal will be without captain Marcos Senna for three weeks because of a leg injury, the club said Wednesday.
Senna, 32, was already unavailable for Wednesday's UEFA Champions League return leg against Arsenal because of the injury.
Now he will also miss the semi-finals if Villarreal qualify.
The Spanish-Brazilian midfielder, who scored in the first leg against the Gunners which ended 1-1, sustained the injury during the Primera Liga match against Malaga on Saturday.
Tests carried out Wednesday morning revealed he had suffered a torn muscle in his left leg.
"Marcos Senna needs three weeks to recover," the club said.