Lamb in England U20 squad
Harlequins back-row Dino Lamb will replace Evans in England's 28-man squad, who gathered in Guildford last week for a pre-tournament training camp.
England U20 head coach Ian Vass said: "It's a shame to lose Will at this early stage however this is a fantastic opportunity for Dino. We are pleased with how the training camp went last week and the players are hugely excited by what is ahead."
Vass, Louis Deacon and Tom Williams continue as England's coaching team, having joined the management as part of a new agreement with Premiership Rugby in which club coaches lead and develop the U20s while gaining experience in an international environment.
Playing all of their Pool A matches in the Avchala Stadium, England will open their campaign against Samoa on Wednesday, May 31.
England will face familiar faces in their second fixture when they come up against Wales on Sunday, June 4. The two sides recently met in the Six Nations, with England coming out 37-21 winners.
Australia, who were in England's pool last year, are the opposition for their final pool game on Thursday, June 8.
England U20 Squad – revised:
Forwards: Ralph Adams-Hale, Josh Bayliss, Jamie Blamire, Josh Caulfield, Justin Clegg, Max Davies, Ollie Dawe, Ben Earl, Ciaran Knight, Dino Lamb, Zach Mercer, Joe Mullis, Jack Nay, Alex Seville, Marcus Street, Henry Walker.
Backs: Sam Aspland-Robinson, Theo Brophy Clews, Will Butler, Ali Crossdale, Gabriel Ibitoye, Max Malins, Alex Mitchell, Dominic Morris, Tom Parton, Harry Randall, Jacob Umaga, Max Wright.
