The club's announcement contradicts a statement released by the German Football Federation which claimed operations had been carried out on both feet.

Chelsea's club doctor Bryan English insisted: "I had a call from the German medical team saying Michael had been playing on Wednesday in quite severe pain down towards the third and fourth toes in his right foot.

"They scanned him the following morning and he had an enlarged nerve in that area which is something that can develop over many weeks and months and suddenly it started giving him pain.

"It is something that if it doesn't give you pain, you leave it alone, but if it gives pain, there is a 20% chance of solving it with injection treatment, but we have taken the option to go for surgery.

"He had surgery, a successful procedure, and it will be about two weeks before he is back in training."

Earlier, the German federation had reported the 32-year-old had an operation to remove a neuroma - a benign nerve tumour - from both feet.

National team doctor Hans-Wilhelm Muller-Wohlfahrt told the DFB's website: "Michael Ballack complained after the World Cup qualifier against Wales on Wednesday repeatedly about strong pains in both feet.

"An MRI scan on Thursday confirmed our suspicions of a neuroma, so after speaking with the club doctor, manager and coach at Chelsea we decided to operate immediately on both feet.

"If the recovery goes normally, Michael will probably be able to return to training in two weeks."

Meanwhile, defender Ricardo Carvalho is back in full training after an injury to the medial collateral ligament in his knee.

But Joe and Ashley Cole remain sidelined with English explaining: "Joe Cole had an awkward external rotation twist to the ankle joint that always causes more problems than the classic example when someone goes over on their ankle.

"The swelling has gone down and he is performing very well in the pool but still has pain on certain movements.

"Ashley has sustained about a five centimetre tear to the hamstring so not insignificant.

"It is unusual for him because he is an extremely fit player when it comes to muscle injuries over the years.

"It is rare for him to suffer this kind of problem, however he has had one or two very minor back issues over the last months so we have got time to address those issues as well. We will aim to have him back for the Liverpool game next weekend."