Mark Wahlberg says he believes in Baker Mayfield -- so he placed a REAL bet on the Cleveland Browns to win 6 games in 2018.
Yeah, he's being serious.
Don't worry, he also made some less risky wagers -- betting on the Patriots and the Eagles to get back to the Super Bowl this season.
Wahlberg also bet on Ronda Rousey -- casting her in his new movie, "Mile 22" ... and he's super fired up about her role in the flick.