David Cone

From Wiki Gonzalez

David Cone pitched for various major league teams from 1986 to 2003. At some point early in his career, it is rumored that he was caught engaging in self-abuse in a bullpen. The exact details are unclear, but may be added to this page in the future.

One theory is he was reading Onan Masaoka's guide to "How to Beat Yourself and Remain In the Big Leagues" (Harlequin Press--out of print)