On Boxing Day, José Mourinho demanded a quick decision from his medical team over the treatment of John Terry’s back injury. What the Chelsea manager wants, he usually gets, and yesterday the England captain underwent a successful operation that is likely to rule him out for three to six weeks.

While it is a significant blow to the Barclays Premiership champions, who are experiencing unprecedented defensive woes, it gives the defender a chance of being fit for England’s friendly against Spain on February 7.

“The operation took place in France following consultation between the Chelsea medical department and a leading neurosurgical specialist,” a club statement read. “The operation to remove a sequestrated lumbar intervertebral disc was successful and everyone at the club wishes John a speedy and full recovery.”

Terry went under the knife — and the laser — in Bordeaux of Dr Jean Destandau, a leading back surgeon who used laser-assisted keyhole surgery to shave off the offending disc.

Another dose of bad news arrived yesterday when it was revealed that the stress fracture in Joe Cole’s foot has not responded to a month’s rest. Cole was expected to return in the new year but he is still on crutches. “I don’t know if the best option is surgery or not,” Mourinho said of Cole’s injury. “At the moment I don’t know how long he will be out.”

Mourinho is paying the price for trimming his squad in the summer. The Portuguese is so short of defensive options that he even considered drafting in Didier Drogba as an emergency centre back. Mourinho sold William Gallas and Robert Huth in August and brought in Khalid Boulahrouz as a replacement, but he has failed to impress, leading to speculation that Chelsea will buy another defender next month, though they may now wait until the end of January, when Terry’s prognosis will be more precise.

Without their linchpin, Chelsea have conceded two goals in each of their past three Barclays Premiership matches.

Phil Sheard, a consultant orthopaedia spinal surgeon, suggested that the club opted for surgery because it offered the quickest route back to fitness for the 26-year-old. “A couple of weeks is the most optimistic. Realistically you are looking at four to six weeks before he will be back playing football,” Sheard said.

“In most cases, these will get better by themselves. But we quite frequently do operations so that we can get people back to work quickly.”

Drogba says that Chelsea’s new defensive vulnerability is a serious problem. “We cannot give the other teams the belief that they can score, that they can win,” he said. “Last season we were very strong when we scored one goal and the other teams could not think about coming back.”

Though the squad may be small, there are too many big characters for Michael Ballack. The Germany midfield player claimed that it is hard to play with his team-mates — because they are excellent.

“I have only been over here for four months,” Ballack, who left Bayern Munich in the summer, said. “I find it more difficult to integrate myself into a team such as Chelsea, where there is a large number of strong personalities. We have 13 or 14 world-class players. I think that I can play better than I have so far.”

Though Ballack appears awestruck by Chelsea’s star power, Mourinho believes that his side will never have the recognition that the biggest clubs like Manchester United have. “On the one hand you’ve got Chelsea’s economic power, but on the other you have the history, the status, the institutional weight of other big clubs who play against us,” he said.