Athletic Bilbao says midfielder Iker Muniain has torn a ligament in his right knee and will require surgery.
Muniain tore a ligament in his other knee in April 2015, knocking him out of competition for nearly a year.
The Spanish club announced his new injury on Friday, a day after Muniain was carried off the field during Bilbao’s 1-0 loss to Ukrainian team FC Zarya in the Europa League.
Now 24, Muniain broke the record for the youngest player to score in the Spanish league in 2009 when he was 16. He is a key playmaker for Bilbao.