Though production is currently underway on Iron Man 3 and Thor: The Dark World, Marvel is also busy filling out the cast of Captain America: The Winter Soldier, which starts filming next March.  Chris Evans is already set to return as the titular Cap, Anthony Mackie has been confirmed as Falcon, and Sebastian Stan is likely coming back to portray the titular Soldier, but further casting has yet to be announced.We know that a number of actresses are vying for the female lead, and just recently we learned that producers are also looking to fill two “very physical” male villain roles.  It appears we have confirmation on one of the characters, as The Grey and Warrior star Frank Grillo has revealed that he’s in the midst of testing for a baddie role in the superhero sequel.  Hit the jump for more details.Grillo took to his Twitter earlier today to reveal that he had been in L.A. at Marvel, all but confirming that he was testing for a role in the Captain America sequel:[EMBED_TWITTER]https://twitter.com/FrankGrillo/status/260474394294497281[/EMBED_TWITTER] [EMBED_TWITTER]https://twitter.com/FrankGrillo/status/260490315729866752[/EMBED_TWITTER] The “bones” hashtag may ring familiar to comics fans, and radio host/comedian Matthew Aaron looks to have revealed the nature of the role Grillo tested for before Grillo even announced the news (via CBM):[EMBED_TWITTER]https://twitter.com/MattAaronShow/status/259794328090718208[/EMBED_TWITTER]'[EMBED_TWITTER]https://twitter.com/MattAaronShow/status/259771510087110656[/EMBED_TWITTER] For those unfamiliar, the character of Crossbones usually appears as a henchman of Red Skull and is a fairly sharp marksman who’s well-versed in hand-to-hand combat.  He's involved in a comics storyline that involves both Captain America and Falcon, so his appearance in the Joe and Anthony Russo-helmed sequel would make sense.Previous reports had Josh Holloway (Lost) and Nikolaj Coster-Waldau (Game of Thrones) also on Marvel's radar, so Grillo appears to be one of a few other actors in contention for the role.  Grillo showed tremendous talent in both The Grey and Warrior, so given these three choices he'd be my favorite.  The actor will be seen in the next few months in Zero Dark Thirty and Gangster Squad.