Henderson has returned to Old Trafford after two impressive seasons on loan with Sheffield United.
The 23-year-old signed a new five-year contract with Ole Gunnar Solskjaer’s side last week and believes he is capable of unseating Spain’s De Gea, who made a series of costly mistakes last term.
Henderson’s fine form also saw him drafted into Gareth Southgate’s England squad for Nations League matches against Iceland and Denmark.
He is competing against Jordan Pickford and Nick Pope in an attempt to make his England debut.
To star for England, Henderson needs to be playing regularly in the Premier League and he warned De Gea that he has not returned to Old Trafford just to sit on the bench.