The Chelsea midfielder was taken away from England's training on Thursday for treatment after turning his ankle.

Although Lampard has struggled for form during the World Cup, he remains a key figure in coach Sven Goran Eriksson's plans and his injury would be a blow to the Swede, who is looking to book his side a place in the semi-finals for the first time in a major tournament since he took charge.

On the other hand, Portugal have also several worries before their game against England takes place after Cristiano Ronaldo missed training on Friday.

The Manchester United youngster sustained a thigh injury during Portugal's 1-0 victory over Holland in the tournament's second round.

"If he's not 100 percent fit (coach Luiz Felipe) Scolari won't play him," Team spokesman Alfonso Melo said.

With midfield duo Deco and Costinha out through suspension, the loss of Ronaldo may hamper Portugal's chances of progressing to the semi-final for the first time since 1966.