FOXBORO –– The Patriots have announced the signing of 39-year-old Junior Seau; to make room for Seau on the roster, fellow linebacker Adalius Thomas was placed on injured reserve.

Seau worked out for New England yesterday evening, and will be asked to step in immediately -- currently, the Patriots have just four healthy linebackers, Mike Vrabel, Jerod Mayo, Gary Guyton and Rosevelt Colvin. Pierre Woods broke his jaw against Pittsburgh on Sunday, and Vince Redd apparently suffered an ankle injury in that game as well. Tedy Bruschi has been limited in practice recently with a knee problem, though he has yet to miss a game.

Thomas broke his right forearm against Buffalo on Nov. 9 and underwent surgery three days later. Because he had not yet been placed on IR, it was assumed there was a chance he would be able to return at some point before the end of the season.

On Wednesday, the team re-signed Colvin to fill in at outside linebacker, where the Pats have had a run of injuries in recent weeks.

Seau, who turns 40 in a little over a month, said during the offseason that if he were ever to play again, it would be only with the Patriots, to finish what the team didn’t finish last year. He affirmed those comments in October, when he met with New England reporters at his eponymous restaurant in his hometown of San Diego.

“It’s only with the Patriots. With the guys in that locker room and the organization, it’s just such a great [time]. I have a place in my heart for them forever, and I wouldn’t want to play for anybody else but the Krafts and [Bill] Belichick,” he said.

Seau’s history with New England has been well-documented: just days after tearfully announcing that he was “graduating” from football in 2006, he signed with the Patriots. But Seau’s season ended in November, when he broke his arm against the Bears. Last year he returned, platooning with Tedy Bruschi at one of the inside backer spots.

As New England advanced to Super Bowl XLII, one of the underlying desires for the Patriots was to get Seau a championship.

After the Super Bowl, he underwent surgery for a torn rotator cuff, revealing that he had suffered the injury in the fourth game of the season.

His rehab included daily surfing, though recovery took longer than expected and Seau would not have been ready at the start of training camp.

USC connection

When Matt Cassel lines up under center against the Seahawks on Sunday, he’ll be looking across the line of scrimmage at a familiar set of eyes: Lofa Tatupu. Tatupu and Cassel were teammates at USC, and the linebacker and the quarterback developed a close friendship that continues today.

“He’s one of my close friends; we actually talk all the time,” Cassel said, though he added that they haven’t spoken this week. “We had a great relationship in college and continue to have a great relationship. Every offseason we usually spend some time together. He’s a great player, a great friend and he’s doing his thing.”

Tatupu, the son of former Patriot Mosi Tatupu, grew up in Wrentham and attended King Philip Regional High. While Cassel was largely on the bench for the Trojans and had to wait for his turn in the NFL, Tatupu was an All-American and Pro Bowl player from his first day with the Seahawks.

Injury report

New England finally had some good news on the injury front yesterday, as DT Richard Seymour (knee) was removed from the injury/participation report. However, fellow D-lineman Ty Warren (groin) missed practice, as did LBs Pierre Woods (jaw), Vince Redd (ankle) and Adalius Thomas (broken forearm) and WR Kelley Washington (thigh).

smanza@projo.com