It's official, Frank Grillo is joining the DC Universe.

Grillo revealed in an interview with ComicBook.com that he wasn't happy with how the Marvel Cinematic Universe handled Brock Rumlow, better known as Crossbones.

Here's what Grillo said about his role in the MCU:

They never told a story [about Crossbones]. The mythology of the MCU and just what Marvel has in its pool of characters, it's so deep. Crossbones was there for a minute, but he was supposed to be there longer, then they went the direction they did.

I think Crossbones serves a purpose, but I think the interesting thing is that if you see how many people around the world have responded to Crossbones, and again, he's on the screen for a very f--king short amount of time, I think there's more there. I think there was more meat on the bone. I was disappointed, which is why I went over to DC.

And, looking at the numbers, Grillo has the right to complain.

Grillo appeared in three MCU films, starring in two, Captain America: The Winter Soldier and Captain America: Civil War, with a brief role in Avengers: Endgame. In addition to this, Grillo reprised the role in three episodes of Disney+'s What If...? and, throughout that time, Grillo's character never really had much of a storyline.

Basically, Crossbones in the MCU is just an undercover SHIELD agent who works for Hydra.

In the comic books, Crossbones has a bigger role. Specifically, he's the one who assassinates Captain America following the events of Civil War as Sharon Carter guarantees the kill.

This isn't to say that Crossbones had an insignificant part in the MCU. Technically, Crossbones was the reason why the plot of Captain America: Civil War started in the first place as his failed suicide attempt helped cast the Avengers in a negative light.

But, it's easy to see how Grillo would've been led to believe that his character had a future in the MCU. Now that this no longer is the case and with James Gunn already spearheading the DCU, it only makes sense for Grillo to side with the other team.

With that said, Grillo's role in the DC Universe is still up for speculation. However, fans believe that he's been cast as either Rick Flag Sr. or Frankenstein in Creature Commandos.

Grillo has been teasing his involvement with the DC Universe for some time after attending the red-carpet premiere of Shazam! Fury of the Gods, which unfortunately bombed at the global box office. This confirmation just seals the deal while also giving more proof that Ron Perlman is joining him as well. The two starred in the 2019 American Western film, Hell on the Border.

Creature Commandos has no release date at the moment as Gunn is still busy working on Superman: Legacy.