There were mitigating circumstances for Pieters. He was plagued for months by a foot injury that forced him to miss the European Championship last June. Friday's league game was his first for PSV since April.
"He worked so hard to get back, and then he got the red card and then the moment happened and everything came out," team spokesman Jeroen van den Berk said in a phone interview, by way of explanation, not as an excuse. "He just lost it for a second."
It's unclear how long his injured arm will keep Pieters from football. Thankfully, this wasn't as tragic as Slobodan Jankovic's self-inflicted injury in 1993. Furious at a call that forced him to sit out a semifinal in the Greek basketball championships, the center for Panionios of Athens rammed his head against a cement block in anger and suffered a broken neck that left him paralyzed. He died in 2006.
And Pieters didn't kung-fu kick and punch a spectator like Manchester United's Eric Cantona in 1995. He didn't thump the referee. He wasn't plain nasty against a fellow professional as Joey Barton, Keane and other players have been. A broken window can be replaced.
"Some people would even argue that he is managing his anger by not directing it at a real live person," sports psychologist Glyn Roberts said in a phone interview. "You could actually say that by breaking a window, by kicking a wall, whatever, you're actually hitting an inanimate object, you're dissipating your anger to some extent. But, of course, it can have unintended consequences."
The tightrope between too much emotion and not enough of it clearly isn't always easy for players to negotiate. In a sport that demands emotion, where anger is often part of the culture, it's a blessing when only windows bear the brunt.
"I lost self-control and vented my frustration in an incredibly stupid manner," Pieters said Monday. "It gradually dawned on me how badly I had behaved. I can still hardly believe it. My behavior was not only out of character but totally unacceptable. I wish to apologize sincerely and unreservedly to PSV, the fans, my friends, my family, actually to everybody."
John Leicester is an international sports columnist for The Associated Press. Write to him at jleicester(at)ap.org or follow him at http://twitter.com/johnleicester