By adding offensive lineman Tyronne Green yesterday, the Patriots created extra competition at the bottom of the depth chart, making this an important camp for some of their key assets.

For starters, the Pats line is coming off another solid season, and the front five are returning en masse. Left tackle Nate Solder, left guard Logan Mankins, center Ryan Wendell, right guard Dan Connolly and right tackle Sebastian Vollmer are expected to retain their full-time roles.

Of course, nothing is locked in, as Brian Waters wrangled away a job in 2011 and Wendell was superior to Dan Koppen in 2012. However, the premier spot on the depth chart at each offensive line position is solid for the time being. Plus, the Pats didn’t select a lineman in a deep draft class, which is a sign they’re happy with their starters.

The competition gets interesting from there, and the versatility of the backups plays into it. After guard Donald Thomas signed with the Colts this offseason, Nick McDonald jumped into the role of the top interior backup, but the signing of Green could give him a push. When healthy, McDonald has been a valued asset as a reserve, so he’ll have a good angle at the main gig off the bench.

The greatest wild card is Marcus Cannon, who was considered a potential second-round pick in 2011 before he was diagnosed with non-Hodgkin’s lymphoma and fell to the Pats in the fifth round. That is now deep in the rear-view mirror, and the greatest question is Cannon’s positional value.

Cannon was a tackle at TCU, but teams showed a lot of interest in placing him at guard before the draft. However, Bill Belichick often has displayed a preference to keep the 6-foot-5, 340-pounder at right tackle, where he did a good job in relief of Vollmer last Thanksgiving against the Jets. Cannon has still taken practice reps at guard, but that was his emergency position last season.