Jim was nearly unstoppable in his career and that alone is enough to secure his greatness as one of the best ever to play the game.
But does that mean his talent/skills projects to all eras with equal amounts of dominance?
IMO, no, and here’s why…
At 6’2” 230lbs, running 4.5/40, Jim was clearly big and fast enough to play in any NFL era (remarkably he never missed a game due to injury). Give him access to the same year-round training and financial benefits and he likely is one of the best backs in the current NFL.
Despite his considerable natural talents, however, he would
unlikely dominate today’s league as much and how long as he did in the 50’s-60s for these three reasons:
(a) the league no longer averages 55-60% runs per game - i.e. less run play opportunities
(b) his physical stature while very good is no longer an outlier against significantly faster/larger front-7s - i.e. less ability to impose physical dominance
(c) up to 25% more games and an additional 18 different coaches/defenses to outplay - i.e. greater risk for injury and scheme challenges
These reasons are less about Jim and more about the evolution of strategy and physics of the modern game. But they do still apply and thusly do not favor workhorse RBs, and over time, even elite ones like Jim.