Tom Brady was the best QB ever, but I think he'd obviously be a net negative at safety or LB.
Come to think of it, if football remained 1-platoon, it would have hastened the athletic (largely black) QB becoming the norm. Not necessarily with Warren Moon, but Randall Cunningham (plus he punted!) and maybe a Rodney Peete would have been serviceable on D. McNair, Culpepper.....idk, imagine Montana or Marino trying to play defense, even f they grew up doing it. Once you get to Vick, he'd be a plus on both sides of the ball (I assume).
It would have been interesting.
A couple of thoughts:
First, there has been a massive revolution in the athletic quality of big-time college football players. Back in 1964 I would guess that you'd be able to find random non-athlete guys on campus who could compete reasonably well with the football players. Today that is not the case AT ALL.
Specialization starts at a VERY young age and the workout programs are extreme.
The position most impacted by the above is obviously QB. The rest all have rough Offensive/Defensive equivalents:
- O-line / D-line
- Linebackers / O-line, TE's, Backs (that is basically biggest/strongest to smallest/fastest
- WR's / DB's
The biggest problem with the above is that the numbers don't quite work out but you could make it work, for example, by having your biggest linebacker play O-line and your biggest DB play linebacker or some such.
QB's are a different thing altogether. Brains, accuracy, and arm strength are the chief requirements for the position with athletic ability completely secondary in most cases.
I have no idea where a Brady/Montana/Marino would fit on an NFL defense. It seems like they'd be more likely to get in the way than to contribute meaningfully.
I think the suggestion above that you would see a lot more athletic QB's and option-type offenses is correct.
I think you'd HAVE to have an athletic QB because wasting 1/11 of your D would be too big of a liability. But that would mean that QB quality would decline so you would see teams run more and throw less.