FOXBOROUGH, Mass. — He might not be sure what position he's playing or how much time he'll get, but Junior Seau knows one thing for certain: He is preparing as if he is going to be on the field for the Patriots Sunday against the 0-5 Titans.

"There's no choice," Seau said. "I have to be ready for Sunday."

Seau went through his first practice with the team Thursday after signing Wednesday, and he said it's about what he expected. Some good, some bad.

"It was fun going out there and taking the steps and getting in the right position," he said. "I am a little sluggish. There are some things I can do better, but for a first day it went well."

The spry Seau, who turns 41 in January, was seen walking around the morning practice during stretching this morning, talking to several players as he got loose, with the spirit of a player half his age. He says he has embraced the diplomat role even after only one session on the field, he said, "just trying to share the love" with his social-butterfly approach.

The locker room Seau is rejoining looks vastly different than when he last was with the team, and even the linebacker meetings rooms only contain a few familiar faces. And because of all the personnel changes, Seau says he has no clue what he'll be asked to do specifically.

"With Bill Belichick, you never know where you are going to be playing," Seau said. "You have to have a little grasp of everything."

"I know what I do miss: stretching with the (Tedy) Bruschis, the (Mike) Vrabels and (Larry) Izzos. My crew is gone."

The good news is that the X's and O's haven't changed much, especially as the Patriots appear to be switching back to more of the 3-4 defense that Seau saw a lot of the past two seasons. Seau knows with so much change to the roster, he could be asked to play inside or outside in both 3-4 and 4-3 schemes; he could appear in the nickel defense or the goal-line group.

"It's the same system," Seau said. "As long as Bill is here, it's the same system.

"I am going to be playing for the Patriots. (Belichick) will give me the package he wants me to play in, and we'll go with that. But as far as … where am I going to play? I have no idea."

Change is part of the only business Seau has known — aside from his brief flirtation this offseason with his TV show, "Sports Jobs With Junior Seau" on the Versus network before returning to the Pats — and he's not shocked at all that half of the veteran defensive players he worked with in 2006 and '07 are gone.

"The numbers are always going to change as far as the personnel (goes). It happens in the league: If you are around long enough, you will be fired. It happens to everyone. And it's not a big surprise to me."

Seau says he isn't being brought in to be a mentor or leader or a father figure in a locker room depleted of a ton of veteran talent.

"I am really not looking at that right now," he said. "Whatever I have to do, I have to assert myself into being the player that I can be. (Getting) into shape and more importantly, being a part of the formula.

"My role is to help this team win."

When asked what Seau brings to the team, NT Vince Wilfork didn't mince words: "A lot of leadership. A lot of these (younger players) haven't had a chance to play with Junior.

"A bunch of guys grew up watching him, as I did, and all of a sudden you get a chance to play with him. You see his preparation, it's just amazing. … You can learn so much from a guy like that."

And could Wilfork imagine playing until he is 40?

"I wouldn't say that," he said with a big laugh.