Kurt Zouma will miss the rest of the Premier League season and Euro 2016 after confirming that he injured his anterior cruciate ligament during Chelsea's 1-1 draw with Manchester United on Sunday.
Zouma landed awkwardly and twisted his knee in the Stamford Bridge turf after battling for an aerial ball during the second half of the match, leaving the field on a stretcher to be replaced by Gary Cahill on 68 minutes.
The France international will this week undergo knee surgery which will rule him out for the rest of the season and the European Championship, Chelsea confirmed
A statement on Chelsea's official website read: "Kurt will undergo surgery in the next 48 hours and is expected to be out for approximately six months."
Interim manager Guus Hiddink confirmed that the Frenchman would undergo scans on Monday to determine the severity of what he admitted looked a "bad" injury.
And Zouma on Monday took to social media to confirm that he will undergo surgery on his ACL this week:
Scan today has shown I injured my ACL. I will have surgery this week & will come back stronger. Thank you everyone for all the messages ��������
- Kurt Zouma (@KurtZouma) February 8, 2016
Zouma has emerged as a key figure during a nightmare season for Chelsea, making 23 Premier League appearances and establishing himself as the preferred partner for captain John Terry at the heart of the Blues defence.
Zouma started 16 of the most recent 19 Chelsea matches in all competitions, displacing Gary Cahill as first-choice alongside Terry.
Cahill, the England vice-captain, will welcome the opportunity to return to the starting XI in Saturday's Premier League clash with Newcastle, even if the circumstances are unfortunate for a teammate.
Chelsea are now thin at the centre of defence after allowing Papy Djilobodji to go out on loan to Werder Bremen in January.
Branislav Ivanovic could deputise if needed, or Hiddink could turn to untested American Matt Miazga, who joined from the New York Red Bulls last month.
But Spain full-back Cesar Azpilicueta told the Evening Standard that he has no doubt Cahill can live up to expectations.
"Gary is one of the veterans of the team. We know his quality and in this squad, it is always important to be ready," he said. "We need everybody, we have big games coming up and all of us have to be ready.''
Zouma's injury could also have an effect on future negotiations with Terry and Cahill, though Azpilicueta expects Terry to give his all for Chelsea amid his contract standoff.
Terry on Sunday made his first appearance at Stamford Bridge since declaring Chelsea would not be extending his contract this summer.
The 35-year-old captain thanked supporters following the draw with United, but said there had been no communication with the club over his future.
The Blues maintain a contract offer could yet be tabled to Terry, who is set to make his 699th Chelsea appearance against the Magpies.
Azpilicueta added: "It's a situation between him and the club. I don't know what's happening. But since I arrived at Chelsea I have learnt a lot from him. I have played alongside him on the left for most of the time, even in training.
"For me, I see no difference in the way he's performing on the pitch, the way he's playing and he is giving everything for the team as always.''
Diego Costa's late equaliser means Chelsea are still unbeaten under Hiddink, but only two of the Dutchman's eight Premier League games have been won.
Midfielder Nemanja Matic praised the recent impact of Costa, who has seven goals in nine games.
"Diego is a very important player for our team," Matic told Chelsea TV. "In the last couple of games he's been doing very well. He's shown he is important for us and he's going to be very important until the end of the season."
Information from Press Association was used in this report.