Tim Tebow's former Florida teammate took drastic measures to confirm he was really saving himself for marriage ... 'cause Brandon Spikes claims he would randomly show the quarterback pictures of naked women to see how he'd respond.
Spikes -- who played alongside the Heisman winner in Gainesville from 2006-09 -- went in depth about the media obsession with Tebow's virginity during the Gators' dominance in the mid-2000s ... and he revealed he did some questionable investigative reporting of his own to prove the guy was, in fact, sex-free.
"I just wanted to see if he was real," Spikes said on Netflix's "Untold: Swamp Kings," according to the New York Post.
"So I would like, you know, maybe have a picture, a nude picture on my phone or something and show it to him just to see how he would react."
The stunt didn't go over too well with Tebow ... and Spikes explained his response led him to believe the whole thing was really true.
"He was like, 'Come on man! Like, you really get a man uncomfortable!'"
"And I was like, 'Oh, he's serious.'"
Tebow's virginity was a major storyline throughout his college and pro career ... and he went on to marry former Miss Universe Demi-Leigh Nel-Peters in 2020.
Safe to say the abstinence paid off.