The Cam Erving experiment at center appears to have ended. The Cleveland Browns are expected to sign former Green Bay Packers center JC Tretter when free agency begins Thursday afternoon.

Tretter opened the 2016 season as the Packers starter and played very well, but he has had trouble staying healthy. He missed his entire rookie season with an ankle issue and hurt his knee in November. In four seasons, he has started 10 games and missed 33 because of injury. He also is coming off a knee procedure in January, though he is expected to recover in time for OTAs.

ESPN 150 ranking: 58th

Grade: C-plus. Moving Erving from a position he is not suited to play is a good thing. Erving struggled too much for the Browns to keep him at center. Tretter can play and is versatile. He simply has to stay healthy. If he does, the grade goes up. The problem is the Browns too often have ignored injury history as a predictor for the future.

What it means: It's always good to upgrade a position, and Tretter is an upgrade at an important position of need. Pro Football Focus ranked him the NFL's ninth-best center in the time he played. If he can stay healthy, he can play. And he played left tackle in college at Cornell. As for Erving, it figures that he either will be tried at right tackle or released. Given the Browns' salary-cap room and the need at right tackle, Erving probably will be in the mix with Spencer Drango and Shon Coleman at right tackle.

What's the risk: Simple -- health. If he's on the field, Tretter is an athletic lineman who can step right in at center. He just has to show he can play an entire NFL season, that he's not prone to injury. If those issues linger, the Browns will have Austin Reiter coming back from knee surgery. They also liked what they saw of Anthony Fabiano at center in the season finale.