Ricardo Carvalho's knee injury could rule him out for up to a month of Chelsea's Barclays Premier League title challenge.

The 30-year-old suffered medial collateral ligament damage during the 1-1 draw with Manchester United yesterday and he was taken off in the 12th minute of the clash at Stamford Bridge, with medical staff estimating the problem will lead to between three and four weeks on the sidelines.

Fellow Portugal international Deco also sustained a tear in his thigh during the warm-up and will be out for a fortnight.

The blow of losing Deco will be softened by the imminent arrival of Brazil midfielder Mineiro as a free agent. The 33-year-old will provide cover for John Mikel Obi in a holding role, with Michael Essien already out for six months.

Despite a solid performance from Alex after coming off the bench against United, it is Carvalho's loss that could be most significant for boss Luiz Felipe Scolari, such is the importance of the centre-back.

"He is a player that is very fast and he smells when the ball is coming," said Scolari last week. "He can read where the ball is going to be and go."

The former Porto defender could return after the next international break and could make the Champions League tie against Roma or the Premier League clash against Liverpool if he takes the full month.