Chelsea will know the extent of Michael Essien’s injury by Friday.
The Ghana midfielder is scheduled to arrive back at the club’s Cobham training ground this week in order for Chelsea’s own medical staff to assess his knee injury.
Essien was forced out of Ghana’s African Nations Cup campaign after hurting his knee during training.
Essien, 27, could be out of action for at least a month according to initial scans undertaken in Luanda.
They are understood to show that he has suffered a partially torn medial collateral ligament in his left knee and damage to his meniscus.
A spokesperson for Chelsea confirmed: “We are aware of the injury to Michael and have been in contact with the Ghanaian national team.
“We will fully assess the injury on Michael’s return to us later this week. Until then we are unable to comment further.”
Ghana’s players feared the worst when Essien, who has only just recovered from a hamstring problem, went down during a training session.
“This is a big blow because Michael is so important to our team,” said striker Matthew Amoah.
“We’ve lost the motor in our midfield, and this is very bad.”
Midfielder Anthony Annan added: “Michael was turning to make a pass when he just went down. There was no contact from any other player but those around him say they heard a click, and then the physios rushed over.”
Essien’s injury is a massive blow to both Ghana and the Blues. Ghana were hoping he would recover from the injury to play some part in their vital group clash with Burkina Faso today – a game they need to win to progress in the tournament.
But if his injury is as bad as first feared, then Essien is likely to miss Chelsea’s Barclays Premier League clash against title rivals Arsenal at Stamford Bridge and the opening leg of their Champions League tie against Joe Mourinho’s Inter Milan.
Meanwhile England midfielder Frank Lampard believes a tactical rethink by Ancelotti has breathed new life into their title ambitions.
Lampard, who scored twice in the 7-2 thrashing of Sunderland on Saturday, insists they have now shaken off the recent poor form that saw them win just one game in five league matches.
Chelsea have scored 12 goals in their last two games after reverting to a 4-3-3 formation.
“We’ve worked on things in training and we are trying to get behind teams a bit more,” said Lampard.
“Maybe we’d become a little bit predictable. Now we’ve livened up, there is more movement in the team and you can tell by the results.
“The way we played against Sunderland was first class. You won’t get many better performances than that.”