Chelsea skipper John Terry is struggling to make their Champions League clash at Napoli.
The Blues captain was left out of the line-up for Saturday's FA Cup fifth-round tie against Birmingham, despite the knee injury which has sidelined him for three weeks improving.
Manager Andre Villas-Boas told ESPN: "We will have to wait and see. At moment there is a 50-50 chance of him making it.
Terry is keeping his fingers crossed he will return to lead Chelsea out on Tuesday night.
"I've been struggling with my knee recently but, hopefully, I will be back in some capacity," he added."He's going to train on Monday and travel with the team. After that we'll make a decision."