Manuel Pellegrini faces a mounting injury crisis as Manchester City embark on what the manager believes is a key week in their season, with David Silva set to miss the next three games including the derby with Manchester United next Sunday and Vincent Kompany in a race to be fit for the meeting with the champions.

Kompany will not be risked for Tuesday's trip to Viktoria Plzen in their opening Champions League group game as the captain recovers from a groin problem, while Gaël Clichy is also a doubt, with Pellegrini's first-choice full-back definitely ruled out of Saturday's Premier League match at Stoke City because of a thigh injury.

While Silva injured a knee in training on international duty with Spain, Pellegrini's other injury concerns are Micah Richard's ongoing recovery from a hamstring problem and Martín Demichelis, who is out for at least six weeks with strained knee ligaments.

Regarding Silva, the manager said: "We will see next week but we will try for the derby. If he is 100% then he can be at that game."

While it is understood that Silva has only a remote chance of featuring against United, Kompany will be assessed when the club return from the Champions League game. "Kompany I think it is a risk to play three matches in one week," Pellegrini said. "He needs two or three more days to be 100%. Demichelis is a long injury, six weeks."

On Clichy's thigh issue, the Chilean added: "Yes, it is not very important. He is missing this weekend."

Of the challenge that faces City once the Champions League starts, Pellegrini said: "It is a big test for all the big clubs who are playing the Champions League or the Europa League. We have seven games in 21 days before the international break in October, after the same thing October to November and the same thing November to December. That is why we have the squad with 22 players."

The manager welcomed the focus on his side's results that this will attract. "For me and the team and the club the pressure must always be the highest pressure to have a good performances in every tournament we play, Premier League, Champions League, Capital One, for me is always the same. The pressure is positive," he said.

After losing 3-2 at Cardiff City in August Pellegrini's side were also flat when defeating Hull City 2-0 in their previous outing. "This was not the best but it is very difficult at the beginning of the season to have the best performances. We have to improve. We played very well in one game [a 4-0 win over Newcastle United], regular in the other game and not so well in the game we lost, but it is the beginning of the season. I am sure that is why we will improve a lot."