Former NFL wide receiver Brandon Marshall played 13 seasons in the league. He made six Pro Bowls and nearly had 1,000 receptions in his career.

The 35-year-old apparently isn’t done with contact sports, though. He’s taking up a career in professional boxing … as a heavyweight.

Marshall announced on Instagram Tuesday that he was launching a career in professional boxing. He’s already been training for his first fight that is set for May (he didn’t name an opponent), and Marshall took some early shots at the heavyweight division’s biggest names during his announcement.

According to Marshall, his goal is to be heavyweight champion of the world.

https://www.instagram.com/p/B3FI6J7lWXu/

Marshall said:

“I’m about to do the unthinkable. Thirteen years, NFL. Thirty-five, phenomenal shape. Just went 24 rounds. I’m about to do the unthinkable. Heavyweight champion of the world. Lotta people that try fail. I promise you. Joshua, Wilder, Ortiz, Fury. All you boys, I can get it. I’m telling you. You’re not that tough, not that strong. Where I come from, and what I’ve been through in my life, I’m built for this. I promise you that. I’ll see you next May.”

While Marshall was a great football player, he’ll be starting at the bottom in boxing and doing so at an age well beyond a boxer’s prime. So, this video won’t even be on the radars of Anthony Joshua, Deontay Wilder, Luis Ortiz, Andy Ruiz or Tyson Fury. But he’s clearly not short on confidence.

Marshall will have seven months to prove that he can actually box. And hey, crazier things have happened.