Analysis: Where does Seau fit in Pats defense?

FOXBORO — The addition of Junior Seau to the Patriots linebacking corps gives them some positional versatility they did not have before the arrival of the 40-year-old veteran.

Seau will provide depth at a position where New England has been lacking. Before his arrival, the Patriots only had three traditional inside linebackers on the roster — Jerod Mayo, Eric Alexander and Gary Guyton. That depth was tested over a three-week stretch earlier in the season where Mayo was sidelined with a knee injury, and likely limited some of the defensive looks New England was able to present. (The Patriots were a 4-3 team almost exclusively while Mayo was sidelined.)

Now, with Seau’s arrival, New England can do a lot more at linebacker, especially when the Patriots are in a 3-4. While Seau won’t be an every down presence, he will likely play much of the same role that Tedy Bruschi played last season when New England was in the 3-4 — Bruschi, in his last season with the Patriots, was a one- or two-down linebacker early, usually coming off the field in third-down and passing situations in favor of Guyton. Look for Seau to fill the same role this season.

If New England chooses to operate out of the 4-3, Mayo will remain the first option at middle linebacker. On Wednesday, Seau sounded like he would have no problem deferring to Mayo in the middle of a 4-3 — he’s already given up his old locker to Mayo, the one near the door to that leads out to the entrance to the field.

“The sky is the limit for the kid. The sky is the limit,” Seau said of Mayo. “He’s a leader on this defense, a guy who is doing a heckuva job in the middle.”

However, Patriots coach Bill Belichick seemed to indicate that Seau’s positional versatility might also allow him to play some outside linebacker, which could also mean a reduction in playing time for Pierre Woods and Rob Ninkovich.

“Junior’s a pretty versatile guy,” Belichick said. “He’s played inside for us on both the strong and weak side. He’s played in our sub defenses. He’s actually played outside. He’s a pretty versatile guy depending on the scheme and what we have called. I’m sure that he’ll work at a lot of different spots like he usually does.”

However, it’s safe to assume Seau’s signing had as much to do with off-field intangibles as on-field production. The energy level that the 40-year-old still has for the game is enough to power a small city — standing next to him, it’s clear that he radiates passion for the game. He’s a terrific locker room presence, especially with younger players.

“I don’t think I have coached too many players — I’m not saying they’re not passionate — but I haven’t coached too many that are any more passionate than Junior is,” Belichick said. “So I think that’s good for all of us. It’s good for him, it’s good for all the players, it’s good for the coaches [and] it’s good for the team. He brings a lot of positive energy and toughness, so those things are all good.”

A year or two ago, the Patriots may not have needed his knowledge and veteran presence as much as they do now. However, Tedy Bruschi, Rosevelt Colvin, Mike Vrabel, Rodney Harrison and Richard Seymour have all left since the close of the 2008 season. (Looking at this memorable Sports Illustrated cover from 2007, it’s hard to believe that less than two years later, Seau and Adalius Thomas would be the only ones left in New England.)

Now, Seau is one of the few defensive veterans left who can guide young linebackers like Alexander, Guyton and Mayo, as well as other young defenders like Pat Chung — who was three years old when Seau entered the league in 1990.

“How much more experience can you get from somebody?” said Chung. “He’s been doing it for years now. Now I know if I have a question, I’m going right to him. I’ve only talked to him since he’s been here for like a couple of seconds, and he’s smart and down to earth, and he seems like he’s ready to help us. No complaints here.”