More help for new defensive coordinator Mike Pettine and filling a void or two on offense figure to be targets of the Buffalo Bills when the free-agent shopping season begins Tuesday.

The Bills could use help at linebacker and safety for a defense that ranked 31st against the run and 26th in points allowed.

Aside from a quarterback of the future, the Bills’ prime offensive needs are at receiver, tight end and guard.

“We will try to be active in free agency,” said Bills General Manager Buddy Nix. “I don’t know how that’ll work out. We’re not going to go crazy and overspend and get ourselves in a bind where we can’t keep some of our own, but we will be a player. We’ll attempt to make moves in free agency to plug some holes.”

The free agency signing period begins at 4 p.m. Tuesday. The Bills got a jump on the signing derby Saturday by reaching agreement on a deal to keep cornerback and kick returner Leodis McKelvin for four more years.

The Bills need a three-down coverage linebacker to replace Nick Barnett, whom they released. Barnett played 92 percent of the snaps last season. The Bills’ incumbent starters are middle man Kelvin Sheppard, who played 46 percent of the snaps, and Nigel Bradham, a strong-side ’backer in the 4-3 scheme who played 36 percent of the snaps as a rookie. The Bills re-signed nickel linebacker Bryan Scott, who played 54 percent of the snaps, which amounted to most passing downs.

Ideally, the Bills could use someone who is knowledgeable in the 3-4 scheme, which Pettine has run his entire NFL coaching career.

The high-profile options: Inside linebackers Dannell Ellerbe of Baltimore and Brad Jones of Green Bay, and rush linebackers Paul Kruger of Baltimore and Connor Barwin of Houston.

Ellerbe, 6-foot-1, 236 pounds, had a breakout season as a first-year starter for the Super Bowl champion Ravens. He played 99 percent of the snaps over the last 12 games. Jones, 6-3 and 230, offers some versatility to play inside or outside in a 3-4 defense. He shifted inside for the first time last season and excelled while starting 12 games.

The Bills have two starting edge rushers in Mario Williams and Mark Anderson. They like Kyle Moore; he had three sacks for Buffalo last season and is due to be a free agent.

Pettine wants flexibility. Williams can play stand-up rush linebacker in the 3-4, but nobody else on the roster is ideally suited for the job. Kruger had 12 sacks over the last 12 games for the Ravens. Barwin had 11.5 sacks in 2011 but slumped to three last season. He says he wants to play for a winner.

If Pettine follows the philosophy of Jets coach Rex Ryan, for whom Pettine worked the past 11 years, there will be some Jets in the Bills’ plans.

When Ryan and Pettine moved from Baltimore to New York in 2009, they brought with them several Ravens to help the rest of the players learn their defensive scheme.

The most obvious candidate could be Eric Smith, the Jets’ third safety last season. He’s soon to be 30 and is a smart player who could help the secondary adjust to Pettine’s scheme. He would come at a modest price, too.

Smith was cut by the Jets two weeks ago, along with linebackers Calvin Pace and Bart Scott. Pace will be 33 in October and played 94 percent of the Jets’ snaps last year. But he’s no longer a productive rusher. He had three sacks last season. Scott, a former star inside backer, will be 33 in August and is coming off toe surgery.

The Jets’ starting safeties, LaRon Landry and Yeremiah Bell, are free agents, too. Landry, 28, made the Pro Bowl last year and will command a big salary. The Bills have to pay Jairus Byrd a big contract, so it’s questionable whether they’d want to have two safeties making big money. Bell is 35. Quality Jets defensive tackle Mike DeVito is a free agent, but the Bills do not have a need at defensive tackle.

Here’s a look at some of the top free agents available by position, with an emphasis on the Bills’ needs:

Receivers: Mike Wallace (Steelers), Greg Jennings (Packers), Wes Welker (Patriots), Danny Amendola (Rams), Mohamed Massaquoi (Browns), Brandon Gibson (Rams), Braylon Edwards (Jets), Jerome Simpson (Bengals). Wallace is one of the game’s best deep threats, but he will cost more than $10 million a year. Jennings reportedly wants that much, too. He has 50 TDs and almost 5,000 yards in the last 5½ years. He’s 29 and missed half of last season with a groin injury. Among the less expensive options are Massaquoi, a former second-round pick with good size who averaged 34 catches his first three years in a stunted Browns offense. Gibson, a four-year veteran with decent size, is coming off his best season (51 catches for 691 yards). Edwards has done little the last two years and has had off-field issues but is big and has had some good years. Simpson is a talent with a checkered past off the field.

Inside linebackers: Jones (Packers), Ellerbe (Ravens), Rey Maualuga (Bengals), Larry Grant (Niners), Brian Urlacher (Bears), Scott (Jets). Jones is a former seventh-round pick. Ellerbe was undrafted. Can Ellerbe be wooed away from Super Bowl champion Baltimore, where he wants to stay? Maualuga, 26, is a two-down inside backer with a lot of talent. He had a down year in 2012. Grant is a former seventh-rounder who backed up Patrick Willis the past two years. Urlacher is 35.

Outside linebackers: Kruger (Ravens), Barwin (Texans), Philip Wheeler (Raiders), Justin Durant (Lions), Daryl Smith (Jaguars), James Harrison (Steelers), Erin Henderson (Vikings), Pace (Jets), Victor Butler (Cowboys), Shaun Phillips (Chargers), Manny Lawson (Bengals), Erik Walden (Packers). Kruger will be hotly pursued and overpriced after his big season with the Ravens. Wheeler, 28, is a former third-rounder who has played in a 4-3 his whole career. He’s a three-down linebacker who played mostly in coverage but showed a glimmer of pass rush. Durant, 27, is a good player who is strictly a coverage ’backer. Harrison, the Steeler great, is soon to be 35. Henderson is a two-down ’backer. Butler is a lower-priced backup who will be targeted by some 3-4 teams.

Tight ends: Martellus Bennett (Giants), Jared Cook (Titans), Delanie Walker (49ers), Dustin Keller (Jets), Brandon Myers (Raiders), Anthony Fasano (Dolphins). This is a good group of players, and the Bills need help at tight end, where starter Scott Chandler is recovering from a knee injury. Bennett, 26, is a capable receiver and blocker who caught 55 passes for 626 yards. Cook, 26, is a former third-round pick who has 93 catches the past two years in half-time duty.

Walker is really attractive because of his versatility. He can play H-back and fullback, too, and he’s an excellent blocker. He has averaged 22 catches the past four years as the Niners’ No. 2 tight end.

Keller, 28, is a big receiver who plays out of the slot. He had 65 catches for 815 yards in 2011 but barely played last season due to injuries. He figures to be expensive.

Myers, 27, is a four-year veteran who had 79 catches in his first full year as a starter in 2012. He’s a willing but no-so-effective blocker.

Guards: Andy Levitre (Bills), Louis Vasquez (Chargers), Brandon Moore (Jets), Kevin Boothe (Giants), Chad Rinehart (Bills), Ramon Foster (Steelers), Deuce Lutui (Titans).

The Bills must be mindful of their desire to retain center Eric Wood, entering the last year of his contract. How much do they want to invest in the middle three of their O-line? Vasquez is a mauler with 54 starts in four years. Yahoo! Sports reported the Bills are among the teams interested in him.

Moore might make sense. As Jets line coach in 2003, Buffalo head coach Doug Marrone converted Moore from defensive line to guard and molded him into a quality player. Moore, who will be 33 in June, has 142 starts. He was a Pro Bowler in 2011 and had another strong season in 2012. He could have a couple of good years left, and he won’t be a huge expense.

Rinehart has started 17 games for the Bills the past three seasons.

Safeties: Dashon Goldson (49ers), Landry (Jets), Dawan Landry (Jaguars), Glover Quin (Texans), Adrian Wilson (Cardinals), Kenny Phillips (Giants), Louis Delmas (Lions), Smith (Jets), Bell (Jets). The Bills need to work out a big-money deal with Jairus Byrd, whose rights they retained with the franchise tag. Da’Norris Searcy is the incumbent strong safety with George Wilson’s departure. Smith seems like a perfect guy to help the Bills’ defensive backs adjust to Pettine’s system. It’s a good year for safeties in the draft.

Quarterbacks: Jason Campbell (Bears), Brady Quinn (Chiefs). Dolphins backup Matt Moore, 28, was due to be a free agent but re-signed with Miami. None of the QBs available is an upgrade over Ryan Fitzpatrick.

Cornerbacks: Sean Smith (Dolphins), Chris Gamble (Panthers), Antoine Cason (Chargers), Keenan Lewis (Steelers), Dominique Rodgers-Cromartie (Eagles), Chris Houston (Lions), Kyle Arrington (Patriots), Aqib Talib (Patriots), Derek Cox (Jaguars), Nnamdi Asomugha (Eagles), Cary Williams (Ravens). This is a pretty deep crop of players. Since the Bills re-signed McKelvin, they probably will look next to the draft for CB help.

Defensive end: Michael Bennett (Bucs), Cliff Avril (Lions), Dwight Freeney (Colts), Kyle Moore (Bills), William Hayes (Rams), Israel Idonije (Bears), Osi Umenyiora (Giants), Trevor Scott (Patriots), Lawrence Jackson (Lions). The Bills’ edge rushers are Williams and Anderson.

Defensive tackle: Desmond Bryant (Raiders), Jason Jones (Seahawks), Richard Seymour (Raiders), Roy Miller (Bucs). It’s not a position of need for the Bills.

Offensive tackle: Jake Long (Dolphins), Sebastian Vollmer (Patriots), Andre Smith (Bengals), Jermon Bushrod (Saints), Phil Loadholt (Vikings), Sam Baker (Falcons). This is a better group of tackles than normal in free agency. The Bills are in good shape at the position, with their top five of Cordy Glenn, Erik Pears, Chris Hairston, Zebrie Sanders and Sam Young.

Running back: Reggie Bush (Dolphins), Ahmad Bradshaw (Giants), Steven Jackson (Rams), Shonn Greene (Jets), Danny Woodhead (Patriots).

Fullback: Jerome Felton (Vikings), James Casey (Texans), Greg Jones (Jaguars). The Bills’ Corey McIntyre is 34. He played just 10 percent of the offensive snaps last year.