David Luiz's continued absence with a knee injury has been explained as a "serious" problem by Chelsea boss Antonio Conte, but he remains hopeful of a swift recovery.
The Brazilian centre-back has been in and out of Conte's team this season, with erratic form an initial contributor to him being dropped by the Italian.
But now Luiz is being forced to miss out with a knee injury, with his last performance coming against Qarabag in the Champions League on November 22.
Conte is hoping that the 30-year-old is able to get over the problem soon, but he conceded that it is by no means a minor issue.
"David has an inflammation in the knee and we are trying to solve this situation with the doctor," Conte told reporters at a news conference ahead of Saturday's clash with Southampton.
Conte reports David Luiz has a big inflammation in his knee and he doesn't know when the Brazilian will be back. — Chelsea FC (@ChelseaFC) December 15, 2017
"It's important to assess the situation day by day and to try to solve this problem. I don't know when he's able to come back, but for sure we are trying to sort his situation.
"The player is working apart [from the rest of the team] and the last days he was outside and in the pool.
"Today he was swimming and out on the pitch to run a bit, but very slowly. This is a serious problem, but we hope to solve it as soon as possible.
"I think every player is frustrated when they don't play, especially when injured. For sure, there's a lot of frustration for the injury and because every player wants to try to put difficulty into the coach's choices.
"I understand, I was a player and when I was injured I was very sad because you want to feel well and be ready for the competition and training. But injuries are part of the job."
Conte is not expecting to have any other selection issues, however, with everyone else at his disposal, including Alvaro Morata after his recovery from a back problem.
"No, there are no new injuries and all the players are available," he said. "No worries about injuries.
"Morata is better and he trained with us two days ago and also today. He has this pain in his back, but he is in contention for the game."
The Spaniard has reportedly been watching clips of Didier Drogba in an attempt to become a better physical presence and, although Conte sees them as two very different players, he has no doubt about Morata's potential.
"I think they're two different players with different characteristics," Conte said. "Drogba brought history to this club and he was a wonderful player and striker.
"I think he was powerful and more powerful than Alvaro, but Alvaro, don't forget, has a lot of space for improvement.
"He's strong physically and technical. I see a great future for Alvaro."