Real Madrid midfielder Luka Modric faces more than a month out of action after an operation to remove a piece of cartilage from his left knee.
When Modric missed training on Saturday, it appeared he was being rested for Sunday's home game against Eibar after completing 90 minutes in the midweek Champions League draw at Borussia Dortmund.
Coach Zinedine Zidane did not mention any problem at his prematch news conference, at which he confirmed that playmaker Isco was set to start against Eibar at the Bernabeu.
But a club statement released on Saturday said Modric had undergone tests on his left knee and a cartilage problem had been discovered.
Another statement, released on Sunday, said the 31-year-old Croatia international had undergone an arthroscopy to remove a fragment of cartilage that had been causing him problems.
"Our player Luka Modric has today undergone an arthroscopy on his left knee to remove a fragment of cartilage of post-trauma origin," the statement said.
"The operation was carried out successfully under the supervision of Real Madrid's head of medical services, doctor Jesus Olmo. Modric will begin his recovery process tomorrow."
The Madrid statement did not say how long that recovery period was likely to be, but it has already been confirmed that Modric will miss the forthcoming World Cup qualifiers against Kosovo and Finland.
Spanish outlet AS reported that he would face more than a month out and miss at least five club games, and said he had been carrying the injury in recent weeks.
Modric has suffered knee problems before and missed a chunk of the 2014-15 campaign with a ligament injury to his right knee.
Zidane is currently without holding midfielder Casemiro and left-backs Fabio Coentrao and Marcelo, although the latter is expected to be back for the game at Real Betis on Oct. 15.