Marvel’s Guardians of the Galaxy may be the 2nd highest-grossing movie of 2014, but it was the Earth-bound, game-changing third act plot twists of Captain America: The Winter Soldier that have had the most immediate and far-reaching effect on the Marvel Cinematic Universe.

Beyond its 1970s spy-movie feel and laying the groundwork for The Avengers: Age of Ultron, the Captain America sequel introduced a host of new characters, including Anthony Mackie’s Sam Wilson a.k.a. Falcon along with the formidable Brock Rumlow – played by Frank Grillo – who fans know as the comic book villain Crossbones.

With the ending of The Winter Soldier setting up Rumlow’s future return – having not yet taken up the identity of Crossbones by that point – it wasn’t much of a surprise to hear that Grillo does indeed have a multi-picture contract with Marvel, though the specifics of when and how he’ll be seen again were left vague. According to Variety‘s Justin Kroll (hat tip to CBM), Grillo’s Crossbones will be the main villain of the 2016 film Captain America: Civil War.

On the heels of the reports that Inglourious Basterds actor Daniel Bruhl has been cast as an as-yet-undisclosed antagonist for Civil War and Doctor Strange, Kroll attempted to clarify Bruhl’s role in the two films with the following tweet:

Beat by Marvel in that one, two things he will play villain but not main one, Crossbones still main

Longtime comic book readers know that Crossbones was responsible for an attempted assassination of Captain America at the behest of the Red Skull after Marvel’s Civil War event – if Rumlow is indeed to be the big bad of the Civil War movie, it begs the question of whether or not Marvel will include this. As for how much Frank Grillo knows about any of this, he tweeted to his own followers that he knows “less than nothing” about Captain America 3.

Marvel’s comic book universe has seen some big changes in the past year: a new female Thor, the death of Wolverine, a new Captain America. And their movie studio now has a freshly-minted franchise in the form of Guardians of the Galaxy, not to mention the potential for more with Ant-Man, Black Panther, Captain Marvel, and Doctor Strange in development.

Their current movie Cap Chris Evans has talked candidly about his post-Marvel career, and the evidence is mounting up for a different roster of heroes making up Earth’s Mightiest by the time the two-part Avengers: Infinity War begins in 2018. Could a dramatic event like the killing off of Captain America at the hands of Crossbones be in store as a way to pivot away from the original characters?

What about you, Screen Ranters? Do you think this could be a strong potential storyline for Captain America: Civil War? Sound off in the comments!

Captain America: Civil War will open in theaters on May 6, 2016.