Conversation so far:
What did Honus Wagner do late in his career?
Wagner won the 1911 batting title by the narrowest of margins.
What sports did Honus Wagner play?
Wagner was an American baseball shortstop who played 21 seasons in Major League Baseball from 1897 to 1917, almost entirely for the Pittsburgh Pirates.
Did Honus Wagner play any other sports besides baseball?
Did Honus Wagner do any coaching in his late career?
After retirement, Wagner served the Pirates as a coach for 39 years, most notably as a hitting instructor from 1933 to 1952.
What else can you tell me about Honus Wagner's late career?
Shortly before the 1908 season, Wagner retired.

Question: Why did he retire?
Self-contained rewrite: Why did Honus Wagner retire?