Athletic Bilbao will be without Ander Herrera for up to six weeks after the midfielder underwent an operation on a recurring hernia injury.
Herrera, 23, has been troubled by the problem for at least six months, and his performances for both his club towards the end of last season, and his country at this summer's Olympics, were seriously hampered.
He has started three games for Athletic this campaign but was withdrawn early on each occasion.
The club confirmed via its website on Friday lunchtime that the procedure appeared to have been carried out successfully.
"The player was operated upon early on Friday morning in Munich by surgeon Ulrike Muschaweck," the statement read. "During the procedure, which took place without complications, the problem known as 'sport-hernia' was corrected.
"Barring any post-operation complications, the player should get the all-clear on Saturday and then return home. The period of recuperation for this type of procedure is typically between four and six weeks."
The playmaker joined the Basque club for €8.5 million from Real Zaragoza in July 2011 and was a key member of Marcelo Bielsa's exciting young team which made the finals of the Europa League and Copa del Rey last season.