The OT situation is as shaky as it gets. Glenn had a poor year last season. Henderson was good for a rookie seventh round pick, but below average for a starting NFL RT. And Kouandjio didn't even dress for most of the season. Those are the only tackles on the team as far as I'm aware.
Bills need it all to break right- Glenn bounces back, Henderson takes a major step forward and Kouandjio turns into a competent NFL lineman. Otherwise, "ground and pound" may very well grind to a halt.