Blake -- a star receiver for East Carolina before joining the Minnesota Vikings in 2021 -- has kickstarted quite the second career after transitioning from football ... he's currently crushing it on the popular competition show.

Now that Blake is in the top 24 on "Idol," we talked to Ricky about watching his talented son on the stage instead of the field ... and he's unbelievably proud, especially considering he had no idea where it came from!!

"It's just amazing because none of us can sing!" Ricky told us this week. "I can't sing, my wife can't sign, my parents, her parents -- it's a gift!"

Ricky -- who played for six teams in the NFL from 1990-2006 -- recalled the first time he heard Blake belt out a tune ... and it was so powerful, he got a frog in his throat.

"For me, it was an emotional moment because I couldn't believe it. Then we heard him in person and we started hearing it more and more and how talented he was and how good he sounded just blew me away in that short period of time."

Ricky said it's super easy to support Blake's new career path ... 'cause he can tell just how much he loves music, just like he was with football.

"I think it took a lot for him to walk away from a game that he loves. A game that his dad played, his brother played and to have the courage to say, 'Hey, Dad, I'm going to pursue music.' I thought that said a lot about who he is as a person and I respect the guy. I love him for that."