UFC Fighter Brendan Schaub Says Tim Tebow Coulda Been UFC Heavyweight Champ!!

Tim Tebow COULDA BEEN THE UFC HEAVYWEIGHT CHAMPION OF THE WORLD ... so says former UFC heavyweight fighter Brendan Schaub.

Schaub -- who's close friends with Tebow -- joined the guys on "TMZ Sports" (weeknights on FS1) to talk about his buddy's athletic prowess.

When asked whether he and Timmy have ever mixed it up in the cage ... Schaub gave a SHOCKING answer.

"If Tim decided when he was younger to pursue the UFC, he'd be the heavyweight champion of the world."