Walker latest to withdraw
The Premier League club have confirmed that the young full-back has an ankle injury. Walker's absence could mean Pearce fields Manchester City's Micah Richards, who was largely overlooked during former coach Fabio Capello's reign.
Pearce already finds himself shorn of the services of strikers Wayne Rooney and Darren Bent as well as Rooney's Manchester United team-mate Tom Cleverley owing to injury.
The striker shortage leaves Pearce with only inexperienced forwards Danny Welbeck, Daniel Sturridge and Fraizer Campbell as his options, unless he opts to draft further names such as Liverpool's Andy Carroll or Tottenham's Jermain Defoe.