Nick Fairley has signed for the St Louis Rams on a one-year, prove yourself deal. When fit and focused, Fairley is one of the NFL's better defensive linemen, but his career has been plagued with concerns about injuries, attitude and his weight. Worth $5million, but with the incentive to make up to $7.5m according to NFL Insider Ian Rapoport, the defensive tackle joins arguably the most fearsome front four in football. The 27-year-old will likely slot in alongside either Defensive Rookie of the Year Aaron Donald or Michael Brockers to aid the Rams' frightening pass rush. Rams coach Jeff Fisher poses with Nick Fairley during his unveiling in St Louis . With defensive ends Chris Long and Robert Quinn, quarterbacks facing the Rams next season - who include Matthew Stafford - will seldom get a moment's peace. Fairley, the 13th overall pick of the 2011 draft, spent the first four years of his career in Detroit, playing 46 games.which yielded 98 tackles, 13.5 sacks, four forced fumbles and three fumble recoveries. But the Lions declined to take up the fifth-year option on his rookie contract and did not exactly bend over backwards to retain his services. A history of inconsistency, injuries and off-field concerns led the Lions to allow him enter free agency. Coach Jeff Fisher made the announcement at a press conference to unveil new quarterback Nick Foles. Fairley injured his knee in the 22-21 win over the Atlanta Falcons at Wembley last year, which ended his season. Following the departure of fellow defensive tackle Ndamukong Suh, the Lions have brought in Haloti Ngata and Tyrunn Walker.
Fairley heads to the NFC West and should play a key part in Jeff Fisher and Gregg Williams' rotating defensive line . The Detroit Lions did not take up his fifth year deal, and Fairley penned a one-year contract worth $5m with incentives to make $2.5m more . The  27-year-old joins one of the most feared front fours in the NFL . When fit and focused he is a disruptive force in the middle . But fears about injuries, attitude and off-field concerns remain .