Hard to have evidence until they play of course, but at some point in life Marino stepped on the field for the first time and was pretty dang good.
So what do we have? We have his rating, 5 star by 247. He was rated as the 5th best QB in the country. He has good size at 6-3, he graded out as a 5 star in his competitions. He was offered by almost all SEC and B10 schools including GA, Bama, Michigan, PSU, Miami and LSU. He finished 5th at the elite 11 and he tied for first in pure passing.
I don't know what more we really can say about the kid, in the BG game as a Frosh he looked pretty damn good.
If your not going to play someone with this pedigree, you should probably move on and just go portal every year. He by far is the most talented QB we have and have had for some time if you go by the services.