A simple look at the Patriots’ depth chart would tell you they are stacked at offensive guard. Starters Brian Waters and Logan Mankins are both Pro Bowlers. Former No. 2 pick Robert Gallery is one of the reserves, along with Ryan Wendell, who has plenty of game experience. And Dan Connolly, who might win the starting center job, is versatile enough to be a starting guard. The Patriots’ backup guards would be competing for starting spots on many teams. However, the OG situation didn’t look very pretty at the start of training camp. Mankins, who partially tore his ACL in the Super Bowl, is beginning camp on the active/PUP list, and Waters continues to be absent. He missed spring practices for “personal reasons,” and the way we hear it, the Patriots were surprised that Waters was a no-show for the start of training camp. Reports indicate that Waters, 35, won’t retire, but it’s a situation worth monitoring.