Let's call A. J. Pierzynski "Nut Job"
From Bruce Jenkins in the San Francisco Chronicle:
One of those now-it-can-be-told stories the White Sox, A.J. Pierzynski's new employer, surely haven't heard: During a Giants exhibition game last spring, Pierzynski took a shot to his, shall we say, private parts. Trainer Stan Conte rushed to the scene, placed his hands on Pierzynski's shoulders in a reassuring way, and asked how it felt. "Like this," said Pierzynski, viciously delivering a knee to Conte's groin. It was a real test of professionalism for the enraged Conte, who vowed to ignore Pierzynski for the rest of the season until Conte realized how that would look. The incident went unreported because all of the beat writers happened to be doing in-game interviews in the clubhouse, but it was corroborated by a half-dozen eyewitnesses who could hardly believe their eyes. Said one source, as reliable as they come: "There is absolutely no doubt that it happened."