John Terry will be out for "approximately three weeks" with a knee injury, Chelsea boss Roberto Di Matteo confirmed on Friday.
Terry escaped serious injury after being forced off on a stretcher during the European champions' Premier League draw at home to Liverpool on Sunday last.
Di Matteo explained: "With JT, we're looking at approximately three weeks. Fortunately, it's not as bad as we first thought. It's an MCL (medial cruciate ligament) strain."
A three-week absence would rule Terry out of the rest of Chelsea's Champions League Group E campaign, starting with Tuesday's crucial trip to Juventus.
He would also miss vital league matches against West Brom, Manchester City, Fulham and West Ham.
He could return for the 8 December trip to Sunderland, the day before Chelsea are expected to travel to Japan for the Club World Cup.
The Blues have struggled badly in defence during Terry's domestic four-match racism ban and Sunday's game was only his second in more than a month.
Di Matteo added: "On the one hand, we're obviously pleased it's not as bad as first feared.
"On the other hand, we're disappointed we're losing him again after he just got back.
"It's a crucial period of the season for us, too. So that's a shame.
"It will depend on the progress of his rehab. We'll do everything to speed it up, but it depends how he reacts as well."
Frank Lampard is still sidelined with a calf injury which has kept him out for three and a half weeks.
Di Matteo said: "We have to be careful with his injury because we don't want to take any risks.
"We want to make sure he's 100 per cent sure to be ready when we bring him back. He's not far off."
Ashley Cole could return from a hamstring problem in tomorrow's game at West Brom.