Chelsea defender Kurt Zouma faces six months out because he needs surgery on the knee injury he suffered on Sunday.
The 21-year-old landed awkwardly after contesting a high ball and was taken off on a stretcher in the 1-1 Premier League draw with Manchester United.
"Scan today has shown I injured my anterior cruciate ligament. I will have surgery this week and will come back stronger," Zouma tweeted.
Chelsea said he would be out for "approximately six months".
The France centre-back has made 32 appearances for the Blues this term.
The most recent of his two France caps was in an international friendly with Denmark in October.
France host this year's European Championship, which begins in June.
Zouma and John Terry have become preferred starters in central defence as Chelsea have gone nine matches without defeat under interim manager Guus Hiddink.
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BBC Sport chief football writer Phil McNulty
Kurt Zouma's serious knee injury is a bitter blow to an outstanding young player, ruling him out of the rest of this season and France's Euro 2016 bid.
It may, however, open the door to fresh possibilities for his two experienced central defensive team-mates at Chelsea, John Terry and Gary Cahill.
Terry reiterated on Sunday that he has had no dialogue with Chelsea since he left the club's hierarchy bemused by announcing he was not getting a new contract and would leave at the end of the season.
Will Chelsea now be tempted to revisit negotiations to buy time and see how Zouma recovers - or is owner Roman Abramovich's mind made up and it is the end of the road for the 35-year-old iconic club captain?
Cahill, meanwhile, was reported as being unsettled in January after falling behind Zouma and seeing his own Euro 2016 prospects being hit by a lack of first-team football.
He will now be right back in the frame, ready to secure his Chelsea future and cement his place in England's plans for France this summer.