Think John Ross' record-breaking 4.22 second 40-yard dash at the NFL combine was impressive??
Well, his speed coach says he coulda gone EVEN FASTER -- claiming he's certain the future NFL wide receiver coulda posted a 4.18 ... had he not cramped at the end of his run.
HE'S NOT KIDDING!!!
TMZ Sports spoke with Gary Cablayan of Evo Sports Training -- who Ross tapped for his pre-NFL speed training -- and he's warning NFL corners ... better ice up.