The Chronicle says that it looks like Antonio Smith is being punished for being late to meetings:

Defensive end Antonio Smith didn’t start the Tennessee game as punishment for being late to meetings. Tim Bulman took his place. “Antonio had a couple of issues with responsibil-ities as far as the team, and so I started Tim,” coach Gary Kubiak said. “Antonio played extremely well.” Asked about the issues, Kubiak said, “Being on time. They all have to follow the team rules.”