'Captain America: The Winter Soldier' begins production in early spring, and Marvel's not wasting any time with the casting. The studio is hard at work to find the perfect actor for the role of Cap's newest foe, and they've started by testing Frank Grillo -- but just which villain is he testing for?

Comic Book Movie picked up this neat little scoop about the 'Captain America' sequel -- it seems that Marvel is currently testing for the lead villain in 'Captain America: The Winter Soldier,' according to various tweets and a tweet from Grillo himself:

That's right -- Grillo, known for his roles in 'Warrior' and 'The Grey,' tested for the role of Crossbone, aka Brock Rumlow. In the comics, Crossbone was a henchman to Red Skull and played a part in the Civil War storyline, which features the Winter Soldier and Falcon -- two characters who are confirmed for the second film and will be played by Sebastian Stan and Anthony Mackie, respectively.

While Hugo Weaving recently said he'd prefer not to honor his contract by returning to the Marvel movie universe, it's still unclear whether or not Marvel will hold him to the contract for this sequel -- or if there's even a part for him in it. And we're not sure if this iteration of Crossbone has anything to do with Red Skull anyhow.

Chris Evans and Scarlett Johansson will also star in 'Captain America: The Winter Soldier,' which is scheduled to hit theaters on April 4, 2014.