Real Madrid midfielder Aurélien Tchouaméni will be out of action for a month, a source has told ESPN, after spraining his ankle in the club's 3-1 Champions League defeat to AC Milan.
Tchouaméni was substituted at half-time in Tuesday's loss at the Bernabéu, with the team trailing 2-1.
Madrid confirmed in a brief statement on Wednesday that Tchouaméni "has been diagnosed with a sprain in his left ankle."
A source told ESPN that the France international was expected to miss four weeks of action.
That would see Tchouaméni absent for Saturday's crucial LaLiga game with Osasuna, as Madrid look to make up ground on leaders Barcelona at the top of the table, and then France's UEFA Nations League matches with Israel and Italy.
He would also miss Madrid's LaLiga game with Leganés, a Champions League tie with Liverpool, and further league games with Getafe and Athletic Club.
Madrid have been hit by a series of injuries to key players this season.
Goalkeeper Thibaut Courtois and full-back Dani Carvajal both missed the defeat to Milan, while centre-back David Alaba is a long-term absentee as he recovers from an ACL tear.
Madrid's players and coach Carlo Ancelotti are under pressure after being heavily beaten 4-0 at home by Barcelona in El Clásico, and then losing 3-1 to Milan.
In the Champions League, they have lost two of their four league phase ties, after they were earlier beaten 1-0 away at Lille.
They also struggled in their other two games, needing two late goals to beat Stuttgart 3-1, and coming back from 0-2 down to overcome Borussia Dortmund 5-2.
In LaLiga, Madrid are nine points behind Barcelona, having played one game fewer after last weekend's game at Valencia was postponed.