UPDATE: Pluck it from the rumour file, he's in! Variety reports that Grillo has won the role of Crossbones. He joins a cast that includes Chris Evans, Sebastian Stan, Anthony Mackie, Scarlett Johansson (at least according to Variety), Cobie Smulders and Samuel L Jackson.

Though this remains one for the Rumour Files until the final decision is made, The Grey’s Frank Grillo has hit Twitter to drop a hint that he has tested for a role in a Marvel film. He followed that up with one about Marvel fans with #bones and then radio host / comedian Matthew Aaron Show added fuel to the fire, saying that Grillo is close to scoring the role of Crossbones, one of the villains in Captain America: The Winter Soldier.

With Joe and Anthony Russo set to start directing the movie in March, casting is naturally in full swing. Grillo certainly seems to fit the physical type for Crossbones, who is often seen in the comics as a henchman of Red Skull and has appeared in Cap’s titles in stories alongside Falcon (who will be portrayed in the film by Anthony Mackie) and Winter Soldier (possibly Sebastian Stan, since Bucky Barnes becomes the Soldier).

Confirmed details are scarce from Marvel themselves, though apparently the film will feature two powerful male villains. Josh Holloway and Game Of Thrones’ Nikolaj Coster-Waldau have also been mentioned as possible candidates, so we’ll have to wait and see who – if any of them – gets chosen.

Captain America: The Winter Soldier is set for release on April 4, 2014.