Chelsea's defensive problems mounted on Tuesday when captain John Terry started consulting doctors over treatment for a nerve problem and Alex was ruled out for as long as eight weeks with a knee injury.

Terry said the injury, which causes pain in his right leg, could keep him out for months. Alex needs surgery to his right knee.

Both missed Chelsea's 3-0 Premier League defeat by Sunderland at the weekend and the defending champion's defense could be vulnerable until the January transfer window opens.

The defeat by Sunderland, Chelsea's heaviest at Stamford Bridge since Russian billionaire Roman Abramovich bought the west London club in 2003, reduced its lead at the top of the Premier League to two points.

"It is at a point where I cannot carry on with it," Terry said. "I used to be able to make it through games because the adrenalin gets you going and you blank the pain out. But now there is no decision to make. After games I'm in agony and not sleeping at all."

British daily The Sun said Terry may travel to Italy for treatment from a specialist recommended by Chelsea manager Carlo Ancelotti.

Chelsea's four-man defense against Sunderland featured three right-backs and such a pattern could continue after Alex was ruled out after linking up with Brazil's squad for a friendly against Argentina.

"Further to the Chelsea medical team's diagnosis, the Brazilian national team doctors agree that further investigation via arthroscopic surgery is required on the player's right knee," Chelsea said in a statement. "That will take place over the coming days."