England and Wasps back row James Haskell is facing four to six months on the sidelines as he prepares to undergo reconstructive surgery on his big toe.
Flanker Haskell was injured during the second Test as England claimed a historic series victory in Australia last month.
The 31-year-old has enjoyed a revival under England head coach Eddie Jones, but will miss the start of the 2016/17 Premiership season.
Losing Haskell is a blow for ambitious Wasps, who will attempt to mount a challenge for domestic and European Champions Cup honours but have also lost new signing Kurtley Beale to injury.
Wasps director of rugby Dai Young said: "We're all really disappointed for James and we are all wishing him a speedy recovery.
"James' performances with England, both in the 3-0 series win over Australia and in England's Six Nations Grand Slam success, have been hugely impressive.
"Everyone at Wasps knows how hard James works to make those performances happen, and we know he'll be working just as hard to come back in the best shape possible.
"Our medical team will be working closely with James over the next few months to get him back to full fitness and in the meantime there will be a good opportunity for the other back row players we have at the club to stake a claim."