"To play a superhero" means to portray or act as a character with extraordinary abilities and heroic qualities in a movie, television show, or play. Full definition
All but one of the actors has previously played their superheroes in other movies leading up to this one. (paulstriptothemovies.com)
Therefore not played a superhero, just be yourself. (1st-attractive.com)
Not every actor who plays a superhero in the Marvel Cinematic Universe has admitted that they'll be among Avengers: Infinity War's 68 characters, but enough have that we can assume everyone who has ever punched a Hydra goon or killed a Chitauri invader — unless they're from Agents Of S.H.I.E.L.D. or the Netflix... (avclub.com)