Kalidou Koulibaly was not part of the Chelsea training session on Monday ahead of their decisive Champions League group stage clash against RB Salzburg tomorrow.
The 31-year-old missed the match against Manchester United at Stamford Bridge on Saturday due to injury and is now a doubt heading into a game that could see the Blues secure qualification to the knockout stages of the competition.
Chelsea held an open training session ahead of the match in Austria, and Koulibaly was not part of the group taking part.
READ MORE: Graham Potter has his 'own Virgil van Dijk' as Chelsea star shows remarkable record vs Man Utd
Ahead of the United game, Potter explained the reason for Koulibaly's absence, saying: "He just felt his knee at the back end of the game against Brentford. It's not too bad, but it's too soon for him to play in this game.
"We lost Koulibaly, so we can't play him, and then we've got a couple of players returning who recovered against Brentford. Thiago couldn't play in the week.
"So it's a case of managing the load and managing the games and picking a team that can be competitive and hopefully win the game."
Chelsea used Marc Cucurella as a centre-back against United, but the Spaniard was subbed off after 35 minutes. Thiago Silva started against Erik ten Hag's side after being rested against Brentford. Meanwhile, Koulibaly, who joined from Napoli earlier this summer, played 90 minutes.
His absence from the substitutes bench meant that Potter wasn't able to field a single defender and limits his options for the away match against Salzburg, the reverse fixture of his first Chelsea game, which ended in a 1-1 draw. Koulibaly did not play in that match either and is now a major doubt heading into a crucial evening.
Should the Blues win they will go onto 10 points and qualify from the group after only taking one point from the opening two matches. Potter's turnaround with back-to-back victories over AC Milan have put the Blues in a strong position.
If Chelsea win and AC Milan beat Dinamo Zagreb, then Potter's side will be confirmed in top spot courtesy of a better head-to-head record over Milan, who would be the only side able to match the 10 points.
Potter will be addressing the media ahead of the match later this evening with a press conference due at 6pm, and more updates will come on football.london from that.
READ NEXT:
Why Mateo Kovacic 'streaked' across Stamford Bridge pitch after Chelsea draw vs Man Utd
Chelsea 'receive' green light to complete January Barcelona transfer amid Todd Boehly contact
Roy Keane gives Kepa Arrizabalaga verdict after late Casemiro goal during Chelsea vs Man United
Chelsea's next five Premier League fixtures compared to Arsenal, Man City, Tottenham and Man Utd
Chelsea news and transfers LIVE: All the latest news, rumours and gossip from Stamford Bridge
