Chelsea head coach Liam Rosenior has suggested that Reece James is likely to spend another period on the sidelines through injury.
The Blues are currently preparing for the second leg of their Champions League last-16 tie with Paris Saint-Germain at Stamford Bridge on Tuesday night.
Trailing 5-2 after the first game in France, Chelsea would have to produce one of the best performances in the history of the tournament to eliminate the defending champions.
Given the deficit, it is unclear how Rosenior will approach the game, particularly when he decided against resting players for Saturday's 1-0 defeat to Newcastle United in a game in which many of his players looked fatigued.
Speaking at a press conference on Monday, Rosenior revealed that club captain James - who signed a new long-term contract last week - was ruled out indefinitely with an injury sustained against the Magpies.
What is Reece James' latest injury?
The Englishman indicated that there was potential for a hamstring suffered by James to be 'quite serious'.
He told reporters: "With Reece, he's felt something in his hamstring at the end of the game against Newcastle.
"Really frustrating and disappointing and one for us, we don't know the full extent of that injury. But that rules him out for tomorrow's game."
When asked it is could be a serious injury, Rosenior added: "It could be. With a hamstring injury, it's never great. And for Reece, hopefully we can just get him scanned, we can find out the full extent and then we know more.
"Because obviously we know what an important player he is, what an important leader he is in the group. He's our captain and also in terms of Malo [Gusto], he's ill today. So we'll have a look at him for tomorrow and the other one.
"Yeah, Estevao is back in training. He'll be a part of the group. We'll assess whether he can take part in the game at some point tomorrow. And with Filip [Jorgensen], he's felt something in his groin after the PSG game. And again, we'll get him scanned to find out the full extent of that injury."
Chelsea handed Neto boost
Meanwhile, Pedro Neto is available for Tuesday's game after UEFA opted against handing the Portugal international a suspension for pushing a ball-boy in the game at Parc des Princes.
Rosenior said: "He's a top player. He's apologised for the incident in Paris. There was no real bad intention from him.
"He wanted to get on with the game and I think UEFA have made the right decision."
With Neto having served a domestic ban versus Newcastle, he will almost certainly be selected in Rosenior's starting lineup versus PSG.