Leigh have taken advantage of the dual-registration system to sign four young players from Super League.
Centurions Coach Ian Millward said: “The four players are going to be training with us and their clubs. Obviously our depth isn’t long so they could be vital to us in having them available.”
He continued: “I’d like to thank both Warrington and St Helens for their co-operation, in making these players available to us.”
Blythe previously played for amateur side Leigh Miners and can play in the back-row or centre, while Mitchell has played almost 30 Super League games for the Wolves in the back row. McCarthy made his debut at the back end of last season and played in Warrington’s Challenge Cup Final victory for Huddersfield, before going on to represent Ireland in the end of season European Cup.