Chelsea’s injury crisis has deepened after the club confirmed defender Ricardo Carvalho is expected to be out of action for at least a month.

But the centre-half could be out for longer, possibly the rest of the season, if he requires corrective surgery on the ankle ligament injury he sustained in the first-half of Wednesday night’s 5-0 victory over Portsmouth.

A spokesman for the club said: “Chelsea can confirm that Ricardo Carvalho suffered ankle ligament damage in the game against Portsmouth. The club will be able to determine over the next 24 hours whether the injury requires corrective surgery, however we can confirm at this point that he’ll be out for at least four weeks.”

His injury leaves Chelsea with just two first-choice central defenders in Brazilian Alex and captain John Terry and comes just days after right-back Branislav Ivanovic was ruled out for a month following a knee injury sustained during the 1-1 draw at Blackburn last weekend.