Which player was the oldest age when they had their most valuable season?
I was a bit shocked today when looking at Phil Niekro's BBREF page to see that his best season by bWAR actually came at the age of 39, where he put up an astonishing 10.0. This got me wondering about the ages in which most players had their best season and who was the oldest at the time. There are plenty of instances of players still playing at a high level into their late 30s/40s (Roger Clemens, David Ortiz, Henry Aaron, Willie Mays, etc.), but all of them still had their best seasons by bWAR in the traditional age period we would expect. So that leaves me with the question, which player