Johnny Manziel -- Brain Fart During Live ESPN Broadcast

He's usually incredible under pressure, but last night Johnny Manziel experienced a live brain freeze moment on live TV ... in the middle of his BCS Championship commentary.

Manziel was on ESPN2 with Tim Tebow to give insight on the Florida St. vs. Auburn game ... when he tried to explain how FSU could contain Auburn QB Nick Marshall in the second half of the game.

That's when Johnny's brain shut down right in the middle of his sentence. It's pretty funny ... even Johnny couldn't help but smile.

But fear not, Manziel recovered like a pro ... and got through the rest of the show without a problem.

Hey, he's not the first guy to have one of those moments on live TV ...