Athletic Bilbao have confirmed that Iker Muniain will miss the remainder of the season with a cruciate knee ligament injury.
The 22-year-old was stretchered off with the complaint during his side's 2-0 defeat away at Sevilla on Saturday night.
A subsequent scan has revealed the extent of the damage, which is expected to keep the playmaker sidelined until around November.
The problem also means that Muniain will be absent for the Copa del Rey final against Barcelona in May.