[Dave W]

I think the poster is referring to statistics - specifically home runs.

[nickcarraway]

Is there some kind of statistical measure that Gehrig would catch up?

I think Babe Ruth had 15 good years as a batter, then was not that great his last year and change.

Gehrig had 12 years+ years he was playing well.

Ruth's physical shape went off a cliff at 38. Gehrig was 35 when he was forced to stop playing. He was certainly in much better shape than Ruth. But it's hard to say, even some healthy players hit a wall in terms of performance.