Johnny Manziel just put on a show in SoCal -- rippin' passes in front of NFL scouts to prove he's ready for another crack at the big show.
It all went down at the University of San Diego's pro day ... where Manziel put on his 1st public showcase since getting cut by the Browns in 2016.
Johnny Football fired off a few dozen passes in front of a larger-than-normal crowd (wonder why?) ... including some end-zone bombs that he uncorked from about 40 yards out!
He also took the time to do a quick Q&A with Fernando Ramirez of NBC San Diego afterwards ... addressing how he's "changed drastically" and is focused on becoming the best version of himself.
Great stuff -- but let it be known that TMZ Sports got his first comeback pass on camera!!