The switch from the 4-3 defense to the 3-4 has led to a change in how the Buffalo Bills view their personnel. Players brought in for the old scheme were forced to change positions and adapt to new roles.

     As a result, new head coach Chan Gailey and defensive coordinator George Edwards are looking to build a roster with personnel that best fits what they want to do. With all positions being closely evaluated, the players know the competition for jobs will be fierce.

     "When you bring in a new coach and a new philosophy, you have to expect changes," said nose tackle Kyle Williams. "Every job is up for grabs, so it's going to make for an exciting training camp."

     Here is a look at some key position battles:

Defensive line depth

    On the roster: Alex Carrington, Rashaad Duncan, Dwan Edwards, Lonnie Harvey, Spencer Johnson, John McCargo, Marcus Stroud, Torell Troup, Kyle Williams.

     Breakdown: The starting ends are Edwards and Stroud, while Williams and Troup will split time at nose tackle. With Carrington and Johnson virtual locks as reserve ends, McCargo's place on the roster is in serious peril. The former first-rounder needs a lights-out camp. Although Harvey won't get as many snaps as Williams and Troup, he can't be overlooked as a possibility to make the 53-man roster. At 342 pounds, Harvey is a true run-stuffer and is surprisingly nimble for a big man. At worst, he should make the practice squad if the Bills decide to keep just two nose tackles.

Poz's ILB partner

     On the roster: Andra Davis, Keith Ellison, Nic Harris, Ryan Manalac, Kawika Mitchell, Arthur Moats, Paul Posluszny.

     Breakdown: The favorite to start next to Posluszny is Davis, one of the Bills' most important free agent acquisitions. He played in the 3-4 with Cleveland and Denver, where he had 90 tackles and 3• sacks last season. His experience in the scheme gives him a leg up on Mitchell, who was limited in the spring while recovering from surgery to repair a torn quadriceps. Even if Mitchell ends up as the No.‚3 man, his knack for timing blitzes up the middle is a strength that will be utilized.

     Ellison and Moats are contending for the fourth spot. Ellison lacks ideal size, but he's an intelligent player who has shown he can adapt to different roles. Moats played defensive end in college, but the sixth-round pick seemed to be making a smooth transition during spring practices. Like Ellison, the undersized Harris was drafted to play in the 4-3. He has some catching up to do after not practicing in the spring while rehabilitating from knee surgery. Special teams play will determine if Harris or Manalac makes the final roster.

Outside linebacker

    On the roster: Danny Batten, Antonio Coleman, Chris Ellis, Chris Kelsay, Aaron Maybin, Aaron Schobel, Reggie Torbor.

     Breakdown: Schobel's expected retirement means Maybin has to step up as a pass-rushing force. The former first-round pick had zero sacks during a disappointing rookie year in which he was undersized and overmatched as a 4-3 end. The 3-4 may be better suited to his talents and he's the projected starter on the weak side. Kelsay is the front-runner on the strong side. While he has embraced the change, he's being asked to do things (like dropping back into coverage) that aren't his forte. How he adjusts bears watching.

     The only challenge to Maybin or Kelsay is Torbor, a late offseason signee. He played inside in Miami's 3-4 defense last season, but has experience at outside linebacker in the New York Giants' 4-3 scheme. He's tough against the run and will push Maybin for snaps on first and second down. Ellis, Batten and Coleman are in the running for the last one or two spots. Batten, a sixth-round pick, got some second-team snaps on the weak side in the spring.

Nickel cornerback

     On the roster: John Destin, Drayton Florence, Dominique Harris, Ellis Lankster, Terrence McGee, Leodis McKelvin, Lydell Sargeant, Ashton Youboty.

     Breakdown: Florence excelled as the third corner behind McGee and McKelvin last season and will be tough to unseat. But Corner has played well when given the chance and can't be ruled out. If Youboty stays healthy, he could compete for a top-four spot. Lankster will challenge for a roster spot if he duplicates his strong camp showing last summer. Sargeant, Harris and Destin appear to be candidates for the practice squad.

Fifth safety

    On the roster: Jairus Byrd, Jon Corto, Cary Harris, Bryan Scott, Donte Whitner, George Wilson.

     Breakdown: The top four are etched in stone with Byrd and Whitner as the starters and Wilson and Scott backing them up. That leaves Harris and Corto to battle for what could be the last spot. Corto is making the transition from linebacker. If special teams is considered, the Orchard Park native has a chance to stick. But can the Bills afford to keep him based solely on his excellence covering kicks and blocking on returns? Harris is comfortable at safety after making the switch from cornerback during his rookie year. He even received some second-team reps in the spring.

awilson@buffnews.comnull