Sports

FREE-AGENT MARKET OFFERS TRENCH WARFARE

The NFL’s free-agent signing period begins Friday. In a three-week series, Post staff writers Paul Schwartz and Mark Cannizzaro analyze this year’s class, position by position. Today: linebackers, and offensive and defensive linemen.

Any team would be happy to have Albert Haynesworth applying enormous pressure up the middle. Take any defensive line in the NFL, add Haynesworth to it, and immediately it is improved.

Come 12:01 a.m. Friday morning, any team likely will have its shot, when the free-agent signing period begins. Haynesworth, who anchored the mighty Titans defense, is the most interesting defensive lineman likely to hit the open market.

The Panthers slapped the franchise tag on All-Pro defensive end Julius Peppers on Thursday, which essentially takes him off the market. But there are other interesting and available defensive ends, such as Bertrand Berry (Cardinals) and Chris Canty (Cowboys). Tank Johnson (Cowboys) – who served a 60-day jail term in 2007 for possessing six guns and ammunition with out a permit – is there for the taking.

As usual, there is a solid group of veteran players on both sides of the line preparing to become free agents.

The Jets last season retooled their defensive line with the signing of Kris Jenkins and added Alan Faneca and Damien Woody to their offensive line. They likely are not going to pay big money for any linemen. The Giants probably will take a stab at a mid-level offensive lineman for depth purposes, with backup center/guard Grey Ruegamer set to become an unrestricted free agent.

The Giants also could be in the market for an interior defensive lineman to help fit into a rotation. At defensive end, Renaldo Wynn and Jerome McDougle are unrestricted free agents.

McDougle is gone and Wynn has a slight chance of returning. The need for an end depends on the decision by the Giants coaching staff regarding the best spot for Mathias Kiwanuka. If Kiwanuka switches back to outside linebacker, where he played for half of the 2007 season before breaking his leg, perhaps Berry, who was solid for the NFC champion Cardinals, would be able to be the third player in a rotation along with starters Justin Tuck and Osi Umenyiora.

There’s a sea change about to unfold in Philadelphia, where for more than a decade Tra Thomas at left tackle and Jon Runyan at right tackle have anchored the Eagles offensive line. The two started a remarkable 134 consecutive regular-season games together. Both are set to become unrestricted free agents and the Eagles will not make a play for both. Runyan, 35, recently had micro-fracture surgery on his right knee and will be out for 4-6 months. That means he likely will miss some or all of training camp.

“The doctor says I should be as good as new,” Runyan told the Philadelphia Daily News. “But I’m not going to be able to prove it until it’s time to play.”

paul.schwartz@nypost.com