Loiselle threw a fastball up and in. Matheny wasn't able to get out of the way and the pitch hit him in the mouth. What happened next (via MLB.com's Adam McCalvy):
Matheny took one step back. He calmly rested his bat on the ground and put his left hand on his hip.
"He never went down, first of all, which is amazing," Vasgersian said. "It was almost like when a fly flies in your mouth. You try to spit it out and go, 'What was that?' Like he was annoyed more than anything."
This was no fly, and home-plate umpire Jerry Crawford and Pirates catcher Jason Kendall knew it. They immediately signaled madly to the Brewers' bench for help.
Said Vasgersian: "He spit out blood, a couple of teeth, probably some cartilage, a chunk of his gums and some grey matter from his brain."
Matheny lost two teeth, got four stitches ... and, at his request, was back in the lineup the next day.
This is why some men can manage baseball teams, and some can't. Well, you probably don't have to be a hard-ass to be a good manager. But it probably helps some.