Italy flanker Sebastian Negri has apologised after his 'crocodile roll' left Jack Willis facing the prospect of a long spell on the sidelines.

Willis had to be driven from the Twickenham pitch on a motorised cart after suffering an agonising knee injury in the final quarter of England's 41-18 Guinness Six Nations victory.

The Wasps turnover king, who moments earlier had scored the fifth of his team's six tries, cried out in agony after his left leg buckled sickeningly as he was pulled out of the ruck by Negri.

Crocodile rolls are permitted by referees as long as they are not around the neck and while there was no act of foul play by Negri, they are a dangerous and controversial technique.

"A quick message to Jack Willis. So sorry about what happened yesterday," Negri said on Twitter.

"Just Horrible and never nice to see. Myself and all the @Federugby boys are wishing you all the best.

"I hope to see you back on the field again soon. Take care and we all know you will be back stronger. Seb"

Willis is undergoing scans to assess the extent of the damage and it is a bitter blow to a destructive flanker who broke into the England team last autumn having battled back from previous knee and ankle issues.

"It's one of those, it's quite emotional," said Willis' head coach at Wasps Lee Blackett, who has had a text conversation with the 24-year-old back row.

"We have seen Jack, for the last few years, come back from his last one, just on the verge of England, then gets himself in this time, and it looked a nasty one. We'll know more come today (Sunday)."