Darnell Dockett took guard Alan Faneca to his back on the play, and while he was down there he grabbed Leinart by the ankles and took him down. This was a non-contact drill, and you really aren't supposed to touch the Quarterback at all. Leinart got up, spiked the ball to the ground in anger, then offensive tackle Levi Brown punched Dockett. Dockett returned the punch, then all hell broke lose.
Bodies started being pushed, punches were thrown, helmets were grabbed. It turned into a brawl.
"I like that," coach Ken Whisenhunt said. "You're looking for those guys to develop that bond or that territorialism to protect their guy."
You don't really want to see a team divided, but seeing defenses / offenses bond, and watching their backs is a good thing. You want each player to have passion for their teammates. You want them to stick up for you in a fight, because that is what a game is every Sunday.
Here is a better angle: