England star Tom Croft is set to miss the rest of this season after suffering a serious knee injury.
The news is a major blow for red rose boss Stuart Lancaster and Croft's club Leicester, coming less than a week into the new campaign.
Croft, who toured Australia with the Lions earlier this summer and has won 38 England caps, was hurt during the closing stages of Tigers' Aviva Premiership victory over Worcester last Sunday.
"Tom had a bang on the knee at the end of Sunday's game which seemed innocuous," Leicester rugby director Richard Cockerill said.
"But it felt sore the next morning and, after further investigation, it appears the damage is to the ACL, the (anterior) cruciate (ligament). He has had surgery on that, and it is likely his season is over.
"It is horrendous bad luck for Tom. He came back from a neck injury last year to play so well for Leicester, England and the British and Irish Lions. But these things happen in sport.
"He will make a full recovery, but it takes time. It is a big blow for him and for us, but we will look forward to welcoming him back when he has fully recovered."
"He will make a full recovery, but it takes time. It is a big blow for him and for us" - Richard Cockerill
Croft suffered a career-threatening neck injury in April last year, yet he returned to action eight months later.
He quickly recaptured top form and forced himself back into England contention, starting the final game of last season's RBS 6 Nations Championship against Wales in Cardiff.
The 27-year-old then continued to impress during Leicester's successful push for the Premiership title and he clinched a place on the Lions' tour to Australia.
Croft featured in all three Lions Tests during the 2009 South Africa tour.
This time around, he started the first Test in Brisbane and went on as a replacement during the second Test in Melbourne.
Lancaster, meanwhile, named Croft in the latest England elite player squad, but he must now press ahead without him, initially during an autumn campaign that features Twickenham appointments with Australia, Argentina and New Zealand.