The Hall of Famer made the bold statement during a recent interview with Men's Health, explaining if Marino were playing in today's era of football -- he very well could have done what Brady did ... and maybe better.

"Put Marino into today’s game where he gets free release ... and his receivers, holy cow, weren't very big," Montana said.

"Now these guys are 6'4, 6'5. I think [Marino] is probably one of the most unsung heroes of the game. People don't talk enough about him or realize the numbers that he put up during the times that he put them up."

Montana also gushed about Marino's tangibles while naming him the B.O.A.T. ... adding, "He had a quick release. I had to step into a lot of things to get enough [force] on the ball."

"He had the perfect torque of his upper body and strength to deliver the ball quickly at a fast release with accuracy."

Now, don't get it twisted ... Montana did note there is a delineation between Greatest of All-Time and Best of All-Time -- though it sure did seem he still believes he holds that crown over Brady as well.

As for who could capture it going forward ... Montana dubbed Patrick Mahomes as the man with the most potential there.