Published: Sep 08, 2012 9:18 PM EDT
Updated: Sep 09, 2012 6:31 AM EDT

ST. LOUIS (AP) - St. Louis Rams middle linebacker James Laurinaitis, one of key pieces in new coach Jeff Fisher's rebuilding plan, has signed a five-year contract extension.

When defensive end Chris Long got a four-year extension on the first day of training camp, the team said Laurinaitis was also a priority. The Rams announced the deal on their Twitter feed Saturday, saying the team was "thrilled to announce" the signing.

Laurinaitis, a second-round pick in 2009 out of Ohio State, has led the Rams in tackles all three of his seasons with double-digit totals every year. He's been durable, too, starting every game.

He has five career sacks and three interceptions.

"I've learned a lot, played a lot," Laurinaitis said during training camp. "Every year I've just tried to get a little bit better, make fewer and fewer mistakes and be accountable."

Laurinaitis is 10 pounds lighter this season, reporting for training camp at 242 pounds, to better handle pass-defending duties in Fisher's system. In his first three seasons, Laurinaitis needed a bigger body to fend of blocks from linemen.

In the offseason, he worked with a nutritionist that provided calorie counts for foods.

"Now, a lot of it is flowing," Laurinaitis said during camp. "Strength has gone up, just a lot more running and functional trainilng."

Fisher has referred to Laurinaitis as a "captain of the defense."