London - Uncapped Wasps flank Jack Willis will miss England's South Africa tour after suffering a serious knee injury that could sideline him for up to a year, the club announced on Tuesday.
The Premiership side said the former England under-20 international sustained "a significant multi-ligament injury" during Saturday's 57-33 playoff defeat at Saracens and is expected to be out for nine to 12 months.
Such a lengthy absence would also end his hopes of challenging for England recognition during the autumn Tests and potentially the 2019 Six Nations.
Willis had to be helped from the pitch following a first-half tackle by Saracens flyhalf Owen Farrell at Allianz Park.
"Following consultation with a specialist, it has been determined that Jack Willis sustained a significant multi-ligament injury to his right knee during last Saturday's Aviva Premiership semi-final," Wasps said in a statement.
Willis, 21, was named in a 34-man squad by England head coach Eddie Jones for the three June Tests in South Africa.
Jones is yet to call up a replacement for Willis.
England squad (33 players without Willis)
Fullbacks/wings: Mike Brown (Harlequins), Elliot Daly (Wasps), Nathan Earle (Saracens), Jonny May (Leicester) Denny Solomona (Sale)
Inside backs: Danny Cipriani (Wasps), Owen Farrell (Saracens, capt), George Ford (Leicester), Alex Lozowski (Saracens), Cameron Redpath (Sale), Dan Robson (Wasps), Henry Slade (Exeter), Ben Spencer (Saracens), Ben Te'o (Worcester), Ben Youngs (Leicester)
Back five: Tom Curry (Sale), Ben Earl(Saracens), Jonny Hill (Exeter), Nick Isiekwe (Saracens), Maro Itoje (Saracens), Joe Launchbury (Wasps), Chris Robshaw (Harlequins), Brad Shields (Hurricanes/Wasps), Sam Simmonds (Exeter), Billy Vunipola (Saracens), Mark Wilson (Newcastle)
Front row: Luke Cowan-Dickie (Exeter), Ellis Genge (Leicester), Jamie George (Saracens), Joe Marler (Harlequins), Kyle Sinckler (Harlequins), Mako Vunipola (Saracens), Harry Williams (Exeter)
Fixtures (17:05 kick-offs SA time)
June 9: South Africa v England, 1st Test, Johannesburg
June 16: South Africa v England, 2nd Test, Bloemfontein
June 23: South Africa v England, 3rd Test, Cape Town