The update on Alex, who had missed both the recent Barclays Premier League games against Fulham and Sunderland, followed news that Terry would continue to see "various specialists" as the former England skipper looked to resolve his long-term problem with a nerve in his right leg.

The defending champions and league leaders saw their makeshift central defensive pairing of Paulo Ferreira and Branislav Ivanovic outmuscled by Sunderland's front line of Asamoah Gyan and Danny Welbeck during Sunday's shock 3-0 home defeat.

Carlo Ancelotti, yet to formally replace axed assistant boss Ray Wilkins, now must plot just how to get through the build-up to a hectic Christmas programme.

The Blues may have already safely qualified for the knockout stages of the Champions League, but now hold only a two-point lead over Arsenal and face a testing league schedule during December with successive fixtures against Tottenham, Manchester United and then the Gunners.

While Terry admits he is unsure just when he will be available again, if all goes to plan with Alex's rehabilitation, the 28-year-old should be back by mid-January.

A statement on the club's website, www.chelseafc.com, read: "Further to the Chelsea medical team's diagnosis, the Brazilian national team doctors agree that further investigation via arthroscopic surgery is required on the player's right knee. That will take place over the coming days.

"Alex is expected to be out for approximately six to eight weeks."

Terry, meanwhile, is set to continue to receive expert medical care in the search for a cure.

"John reported for training this morning. He met with club doctors and the medical team and discussed plans to continue seeing various specialists to try to find a solution to the nerve problems he has been experiencing in his right leg," a Chelsea spokesman confirmed.

Terry was already set to miss England's friendly against France at Wembley tomorrow night, and it has been suggested the defender could fly out to Italy later this week in the search for help.

"It is at a point where I cannot carry on with it," Terry said.

"I used to be able to make it through games because the adrenalin gets you going and you blank the pain out.

"But now there is no decision to make. After games I'm in agony and not sleeping at all."

Terry admits he is concerned over when he may be able to return to full fitness.

"I am at my wit's end," added the former England captain.

"I know I won't play against Birmingham on Saturday, but beyond that there are no clues.

"It could be weeks, it could be months."

Should Terry be ruled out it for an extended spell as feared, it would be another major injury blow for Chelsea who have already been without fellow England international Frank Lampard for most of the season.

Lampard is set to miss at least another two weeks after suffering an abductor muscle injury in training.

Midfielder Michael Essien, meanwhile, has two games to run on his suspension after receiving a straight red card against Fulham.

Full-back Ashley Cole also misses the France international after being withdrawn from the national team squad because of an unspecified injury.

England manager Fabio Capello today confirmed Arsenal youngster Kieran Gibbs will start at Wembley.

Earlier this season, Cole joined Kenny Sansom as the most capped England full-back and has an array of domestic medals from his time both at Highbury and Stamford Bridge.

However, Cole is all too aware the next generation are waiting in the wings, but feels his commitment to the cause burns bright as ever.

"You do get a bit reflective at this stage in your career," Cole told the London Evening Standard.

"There are a lot of youngsters coming through - we have Josh McEachran, who is 17, and you sit with him thinking: 'How old are you?'

"You do feel your age, but being on the pitch makes me feel young and enthusiastic and healthy. That's what keeps me going every day in training.

"I am just doing my job - playing as well as I can for Chelsea and trying to win things.

"I try my best for England, too, and what people think is out of my hands. I can't do anything about it."