Leicester Tigers prop Martin Castrogiovanni will be sidelined for at least four weeks by a knee injury.

Head coach Pat Howard admitted it was "a massive blow" with Tigers entering the final third of the season still challenging for honours in the Guinness Premiership, EDF Energy Cup and Heineken Cup.

Castrogiovanni, who has proved a big success in his first season in English rugby, was injured in the opening stages of last weekend's RBS 6 Nations match between Scotland and Italy, on the occasion of his 43rd international cap.

"It is a medial collateral ligament injury to his knee and we are talking about him being out for a minimum four weeks," said Howard. "He came back to us on Sunday after the injury and our medical team are being very proactive with it.

"It is a massive blow because he has been in fantastic form for the club and we would love to have him available. But we have a lot of depth in the squad and now someone has to step into the breach."

Lewis Moody (shoulder) and Henry Tuilagi (arm) are the other Tigers forwards currently ruled out of action by injury.