You can usually tell by the end of the season whether a QB will make a living with his arm or with his legs (or neither, he won't make it at all).
Those exciting rookies who tuck the ball and run ("mobile") go 1 or 2 seasons until they're so banged up they have to stop running and start throwing, or perish.
That's where RG3 is now.
Yeah it’s sad. I like the guy, but he’s a victim of the NFL marketing execs. They are pushing a style that cannot last in the NFL....unless they want really bad passers who make the quarterback position a shorter career than the typical running back. I am from Philly and have seen enough of this crap going all the way back to Randall Cunningham in the 80s and early 90s. Sure it was fun at times, but you knew we’d never win the whole thing. Year after year we were stuck with these guys while year after year the true pocket QBs won it all.