LONDON (AFP) - Avram Grant will use Chelsea's Champions League match against Valencia on Tuesday to fine-tune his plans for life without Didier Drogba.

Drogba had knee surgery on Saturday to cure a long-standing problem that has bothered him on and off all season and will be sidelined for at least a month.

That will rule the Ivory Coast striker out of the busy Christmas programme which includes a Premier League clash against Arsenal and a League Cup tie with Liverpool.

Even if he is fit by the New Year, Chelsea are unlikely to see Drogba until February as he will join up with his country for the African Nations Cup in January.

Losing such a talismanic player for two months would be bad enough but the erratic form of his potential replacements makes it an even bigger blow.

Andriy Shevchenko scored in Saturday's win over Sunderland but the Ukrainian has struggled so badly at Chelsea that it's hard to imagine he will be able to replicate Drogba's goal tally.

Peru's Claudio Pizarro was signed to provide the kind of physical threat that is Drogba's trademark but he has scored only once so far.

If those two or Salomon Kalou can't fill Drogba's boots they could be out of the running at home and in Europe by the time he returns.

Chelsea have already clinched first place in Group B, so Grant will use the Valencia game to take a look at some different options.

Grant acknowledges Drogba won't be easy to replace but he is convinced his squad havve enough quality to cope.

"It's not going to be easy without Drogba but I didn't plan for an easy life at this club," Grant said.

"We didn't want him to be injured, the operation looks good though. It's not easy but we need to win games anyway.

"We have other types of strikers. The best squad is when you have four strikers who are different to each other and we are prepared.

"That is the reason Shevchenko, Pizarro and the others are in the squad."

It had been claimed that Drogba wanted the operation immediately so he could be fully fit for the African Nations, while Chelsea supposedly wanted him to wait.

But Drogba made it clear the operation couldn't wait and insisted he was determined to play for the Ivory Coast.

"The club did not want to put me in danger. If I had the chance to carry on, I would have done," he said.

"Since I started wearing my country's shirt, everyone knows there is no question of preventing me from contesting this tournament.

"Do you realise what it means to an African and to me in particular? No manager will be able to stop me from playing."

Valencia gave Chelsea a tough time despite losing to the Blues in the quarter-finals last season, but they are a much less daunting proposition now.

They have lost eight of their last 13 matches and are already out of the running to qualify alongside Chelsea. Only a win in London would give them hope of salvaging a UEFA Cup place, but even that depends on Schalke slipping up against Rosenborg.

Ronald Koeman's side have struggled in domestic action as well. Saturday's goalless draw against Osasuna left them 10 points behind La Liga leaders Real Madrid.

Koeman took over from Quique Sanchez Flores in October but has been unable to banish the sense of lethargy that has surrounded the club for much of the campaign.

Valencia's veteran goalkeeper Santiago Canizares admits it has been hard to stomach the bad run, but he believes they will only improve if they stop feeling sorry for themselves.

"Whether the results are fair or unfair, we must accept what is happening. When things are going badly we are frustrated and hurt and we want to do well. We have to move forward," he said.