Athletic Bilbao says 21-year-old defender Yeray Alvarez has a testicular tumourand will undergo surgery next week.
The Basque club said Friday the tumourwas detected in tests conducted a few days ago after the player complained of discomfort.
Team doctor Josean Lekue said at a press conference that although further tests are required, there was reason to be optimistic.
It wasn’t clear how long Alvarez will be sidelined.
The central defender made his debut with the senior squad a few months ago and had been praised as one of the team’s top players this season.
Athletic is seventh in the Spanish league entering the winter break.
Several players and teams across the league expressed their support to Alvarez through social media.