Eight-year veteran Chris Kelsay no longer has to worry about whether he'll fit in the Buffalo Bills new defensive scheme after the converted linebacker signed a four-year contract extension worth about $24 million.

Kelsay revealed before practice Wednesday he had signed the extension a day earlier and is now locked up through the 2014 season.

"I'm thrilled. I wanted to end my career here and this gives me an opportunity to do that," Kelsay said. "Obviously, it still comes down to production and putting it out on the field."

Buffalo's second-round pick out of Nebraska in the 2003 draft, Kelsay is tied with two others as the second longest-serving member on the current roster behind punter Brian Moorman, a 10-year veteran. Kelsay is a defensive captain and has proven durable over his career, during which he's missed only two games due to injury.

He was entering the final season of his existing four-year deal, which is scheduled to pay him a $3.7 million base salary.

There were questions about how Kelsay would make the switch from defensive end to outside linebacker as the Bills introduced a 3-4 defensive scheme this offseason under first-year coach Chan Gailey.

Kelsay won the starting job despite missing a few weeks with a shoulder injury in training camp. He currently ranks third on the team with 19 tackles in three games as the Bills (0-3) prepare to host the New York Jets (2-1) on Sunday.

"I think they kind of wanted to do their homework to see how I fit into this system before anything was done," Kelsay said, noting the team approached his agent about an extension about three weeks ago. "Obviously, they thought highly enough about me to offer me the deal. And I feel very honored that they did so."

The extension was also regarded as vote of confidence for Kelsay, as it came from a new regime that's headed by first-year general manager Buddy Nix.

Kelsay is a seven-year starter, who has 22 sacks, three interceptions and five forced fumbles in 113 career games. His best season came in 2006 when he was credited with 88 tackles and posted career-highs with 5½ sacks, 14 quarterback pressures and 16 quarterback hits.

In other news Wednesday, starting defensive end Marcus Stroud missed practice due to a sore ankle he hurt in a 38-30 loss at New England last weekend. Without providing any details of the injury, coach Chan Gailey said there's a possibility Stroud may not play against the Jets.

On the bright side, starting middle linebacker Paul Posluszny returned to practice and declared himself likely to play Sunday after missing the past two games with a sprained right knee.

"I think there's a great chance of going," Posluszny said. "I'm really excited about how my knee felt."

The Bills defense has struggled without Posluszny, having allowed a combined 62 points and 801 yards in its past two games, including a 34-7 loss at Green Bay on Sept. 19.

Linebacker Kawika Mitchell spoke to reporters for the first time since being placed on the season-ending injured reserve list due to a foot injury on Sept. 10.

Wearing a protective boot, Mitchell said he severely sprained his left foot when a teammate stepped on it during practice. Mitchell didn't require surgery, but said doctors projected it could take up to 12 weeks to heal.

It was a disappointing end to Mitchell's season after the eight-year NFL veteran missed the final 11 games of last season with a right knee injury.

"It's extremely frustrating," Mitchell said. "After going my whole career and whole life, basically, not being injured, and then having to face this two years in a row, it's a little unreal. But in actuality, it's reality, so I'm just dealing with it."

NOTES: LB Andra Davis (shoulder) and TE Jonathan Stupar (foot) both missed practice. ... Rookie RB C.J. Spiller was named AFC special teams player of the week after scoring on a 95-yard kickoff return against New England. ... Jets coach Rex Ryan confirmed to Buffalo reporters on a telephone conference call that New York placed a claim on QB Trent Edwards after the former starter was released by the Bills on Monday. Edwards was awarded to Jacksonville because the Jaguars (1-2) have a worse record.