Real Sociedad's on-loan midfielder Esteban Granero faces a lengthy spell on the sidelines after tearing his anterior cruciate ligament.
The 26-year-old - who joined Jagoba Arrasate's side on a temporary basis from Queens Park Rangers in the close-season - twisted his knee after being introduced as a late substitute in Sociedad's 2-0 UEFA Champions League home defeat to Shakhtar Donetsk on Tuesday.
He had to be carried from the field and the Basque club had earlier announced that the former Real Madrid man was to undergo tests to assess the injury.
And they have now confirmed that the initial prognosis of an ACL rupture proved correct.
A statement on Sociedad's official website read: "The MRI scan done this morning discovered a ruptured anterior cruciate ligament and medial meniscus injury in Granero's right knee.
"This injury will require surgical repair. The player will perform a physical therapy focused on stimulating and maintaining the neuromuscular control of the joint."
Granero signed for QPR in August last year after failing to establish himself at the Bernabeu, but endured a disappointing first season at Loftus Road as the London club were relegated from the Premier League.
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