Packers' offseason roster review: D-line strong with Letroy Guion, B.J. Raji

GREEN BAY, Wis. -- This is the sixth in a series looking at the Green Bay Packers' offseason roster by position as they head into organized team activity practices later this week.

Previous installments: Quarterbacks, running backs, receivers, tight ends, offensive line.

Next up: Defensive line.

Who they added: Christian Ringo (sixth-round pick), Lavon Hooks (undrafted rookie).

Who's gone: Luther Robinson.

Key holdovers: Josh Boyd, Mike Daniels, Bruce Gaston, Letroy Guion, Datone Jones, Mike Pennel, B.J. Raji, Khyri Thorton.

Roster spots likely available: Five or six.

Competition: Last year, the Packers planned to split nose tackle snaps between Raji and Guion, but Guion ended up starting every game after Raji sustained a season-ending torn biceps tendon during the preseason. Guion more than held his own and posted career bests in tackles and sacks (four, including playoffs). With both back under one-year contracts this season, the two should battle for playing time unless the Packers decide to move Raji back to end. In that event, a starting trio of Daniels, Guion and Raji might help them improve against the run, where they were ranked last in the NFL halfway through last year before they rallied to finish 23rd.

Notable: It would have been difficult for the Packers to keep Thornton on the roster last season given how far away he was from contributing as a rookie. But you don't want to cut a third-round draft pick, either. So the hamstring injury Thornton sustained late in the preseason allowed the Packers to stash him on injured reserve. ... Boyd, a fifth-round pick in 2013, has played almost as many defensive snaps (530) the last two seasons as Jones (645), who was a first-round pick in that same draft. ... Robinson, an undrafted rookie who first came to Green Bay as a tryout player during rookie camp, was promoted from the practice squad last October and appeared in five games before he was released earlier this month. He sustained a calf injury late in the season and was placed on injured reserve on Dec. 8.