After featuring for England in their historic win against New Zealand at Twickenham last December; Morgan has suffered a frustrating time with injuries.
After starting England's RBS 6 Nations opener against Scotland, Morgan limped off at Twickenham and was not seen again during the tournament - the injury perhaps ended the Gloucester man's hopes of touring with Warren Gatland's Lions this summer.
Morgan is now back to his best but faces an almighty tussle with London Wasp new-kid on the international block Vunipola for the England number eight jersey.
Both men posses a ball-carrying ability and physicality that no other back-row forward can match on the plane to Argentina and after England's humiliation at the hands of Wales in the Grand Slam decider in March - Lancaster is desperate to unleash his weapons on the Pumas.
He said: "I have 10 caps and I suppose that does make me one of the experienced guys in the current squad.
"Billy [Vunipola] and I have similar weights programmes and while there is rivalry, you need to put that to one side to benefit the team. It doesn't matter who starts against the Baa-Baas, you need to be ready.
"We get on well and both want to help the team."