Tottenham midfielder Moussa Sissoko is expected to be out for at least three months after undergoing knee surgery.
The France international suffered medial collateral ligament damage in the 1-0 Premier League defeat to Southampton on New Year's Day and missed the 1-1 FA Cup draw with Middlesbrough last Sunday.
Spurs expect the 30-year-old to be unable to resume training until the beginning of April.
"Following a clinical assessment and scans, Moussa Sissoko has today (Tuesday) undergone surgery to the medial collateral ligament in his right knee," Spurs said in a statement.
"The France international sustained the injury in our fixture against Southampton, resulting in him missing our recent FA Cup tie at Middlesbrough.
"Our medical staff will monitor Moussa's recovery before he commences rehabilitation with a view to returning to training in early April."
Sissoko has made 26 appearances for Spurs in all competitions this season, scoring in the league wins over Bournemouth and Burnley.
His injury could make him a doubt for Didier Deschamps' France squad for Euro 2020, with the world champions beginning their campaign against Germany in Munich on June 16.
The loss of Sissoko could also impact Spurs' plans during the January transfer window, with three other midfielders linked to moves away from north London.
Christian Eriksen is reportedly a target for Inter, while Harry Winks is said to be of interest to Manchester City and Manchester United and Victor Wanyama had been expected to leave after making just four appearances all season.
However, head coach Jose Mourinho could be reticent to let too many midfielders leave while Sissoko is unavailable, unless at least one replacement can be brought in.
With Sissoko missing, Mourinho will continue to lead Spurs as they attempt to overcome a slow start and secure a top-four finish in the Premier League.
Mourinho was appointed as Tottenham's manager in November on a four-year contract, replacing the sacked Mauricio Pochettino.
Spurs currently sit in sixth place, trailing fourth-place Chelsea by six points.
Mourinho's men face a daunting challenge in their next league match when they face runaway leaders Liverpool at Tottenham Hotspur Stadium on Saturday afternoon.