Kevin Brown almost made the list – he had 22 starts at age 39 for the Yankees in 2004.
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And had he not been a meathead and attacked that dugout wall in Baltimore, chances are he makes the list

Wells, Clemens and Mussina were nowhere near retirement when they joined the team, though.

I suspect that pitchers (and non-pitchers) are playing longer and more effectively as a result of improved training techniques, better nutrition, and greater monetary incentives to pitch longer.

It would be interesting to see if there is any empirical data to support or refute that view.