[Syd Thrift]

Aging would be the closest you can get. You *may* be able to set a hard cutoff on age at, say, 35, but I don't think that's what you're looking for exactly either.

Honestly I hate to say this but, having done a fictional league last season in the 19th century, you're probably best off manually editing in career ending injuries, especially for pitchers. With pitchers, I'd say basically look at the injury, and if it doesn't look like something you can just heal by telling the guy to rub some dirt in it and take a few days off, make it a career-ender. Torn labrums and rotator cuffs are pretty obvious but up until, jeez, Cy Young I guess, you really, really did not see pitchers pitching into their 30s (IIRC Pud Galvin may have? Also Tony Mullane?). Hell, you often didn't see guys pitching past the age of 25. Old Hoss Radbourn was 28 and 29 when he led the league in wins and earned his nickname.

There were hitters who did play longer - Cap Anson in particular hung around the league and was successful long enough to pick up 3000 hits, and King Kelly also lasted a pretty long time considering his somewhat insane lifestyle (his last season in the league IIRC he hired a young man, I believe referred to in the press as "his Mikado" to constantly hover about him with a cigar ready to light in case the one he was smoking ever ran out). You'd probably still want to take their injuries on a case by case basis...