When the Jets introduced Eric Mangini as their new head coach yesterday,Bill Belichick cast a long shadow over the room. Belichick, who has won three Super Bowls since he spurned the Jets to become the head coach of the New England Patriots, has served as Mangini’s mentor for the last decade, and the Jets’ front office hopes that Mangini can replicate the success Belichick has enjoyed in New England.

But an overlooked part of Mangini’s resume is the one season he spent in the NFL when Belichick wasn’t his boss. In 1996, Mangini coached on the staff of the Baltimore Ravens, whose defensive coordinator was Marvin Lewis, now the head coach of the Cincinnati Bengals. An examination of Lewis’s tendencies as a defensive coach could give some hints about what kind of defense Mangini will run with the Jets.

The Lewis defense relies on an athletic middle linebacker who can make plays all over the field, and on defensive linemen who can occupy blockers to keep the middle linebacker free. The season Mangini spent in Baltimore was the rookie year of Ray Lewis, who later became the league’s defensive player of the year and Super Bowl XXXV MVP.Jets middle linebacker Jonathan Vilma is an athletic, hard-hitting powerhouse much like Ray Lewis, and Mangini will likely use Vilma in much the same way.

Rob Ryan, who worked with Mangini for four seasons as the Patriots’ linebackers coach and has spent the last two seasons as the Oakland Raiders’ defensive coordinator, is considered the front-runner for the same job with the Jets. But much like Mangini, Ryan’s defensive pedigree includes more coaches than just Belichick – and like Mangini, Ryan will surely have big plans for Vilma.Ryan is the son of Buddy Ryan, the defensive coordinator of the 1985 Bears, whose famous 46 defense also relied heavily on an athletic, playmaking middle linebacker, Hall of Famer Mike Singletary.

Although the Jets know Vilma is the most important part of the future of their defense, they have big questions elsewhere.Veteran cornerback Ty Law’s contract includes a huge bonus that will force the Jets either to release him or agree to a new deal to fit him under the salary cap.Mangini coached Law for five years in New England, and his presence makes it more likely that the Jets will try to reach a deal to keep Law.

Another pricey veteran,defensive end John Abraham, will be a free agent this off-season. Ryan’s schemes are great for a pass-rushing defensive end like Abraham – Derrick Burgess had a leagueleading 16 sacks this season in Oakland – but Abraham will likely command a large salary,and it is unclear whether the Jets will give it to him.

Whether or not Abraham stays, the Jets will have some changes on the defensive line. James Reed, who has played every game for the last five years at defensive tackle, isn’t a great fit for a defense that will spotlight Vilma. Middle linebackers need bigger linemen fill up space and occupy blockers, and Reed, at 6-feet and 286 pounds, is one of the league’s smallest defensive tackles. Even though Mangini was himself an undersized nose tackle in college at Wesleyan, he’s unlikely to want one as small as Reed.

Just as some questioned whether Belichick could emerge from Bill Parcells’s shadow a decade ago, it’s reasonable to ask whether Mangini’s tenure under a defensive coach like Belichick has given him the necessary experience to become a head coach. But Mangini said at his press conference yesterday that he, not Belichick, ran the defense in New England. “I called every single play last year,” he said.

Mangini, who will turn 35 tomorrow, is the 15th man to become an NFL head coach before his 35th birthday. The list of head coaches who were younger than Mangini when they were hired includes Don Shula, John Madden, and Jon Gruden, all of whom went on to win Super Bowl titles. Bill Cowher was 34 when he took the reigns in Pittsburgh,and he will lead the Steelers into the AFC Championship on Sunday. So age shouldn’t be a concern to Jets fans.

What should concern Jets fans is whether the team has a legitimate plan to rebuild its offense. The six years Mangini spent watching tape of his AFC East rivals have informed his opinion of quarterback Chad Pennington, who has shown flashes of greatness but has never played a full season. Mangini seemed confident yesterday in Pennington’s talent, but not in his health.

“I think Chad Pennington is a great competitor, I think he’s a hard worker, I think he’s smart, and I respect all the things he’s done,” Mangini said. But he added, “I haven’t talked to the doctors.”

Pennington has said he expects his shoulder injury to be fully healed in time for training camp, but the Jets will likely bring in a veteran quarterback in the offseason. Drafting a quarterback who can contribute right away is unlikely because the Jets pick fourth in the April draft,and the two elite quarterbacks available, USC’s Matt Leinart and Texas’s Vince Young, are expected to be taken within the first three selections.

New Orleans Saints offensive coordinator Mike Sheppard, who was on Belichick’s staff with Mangini in Cleveland, is considered the front-runner to become the Jets’ offensive coordinator.Sheppard believes in stretching the field with long passes, whereas Pennington’s strength is his accuracy on short passes, so the two aren’t necessarily a good fit.

Just as no one knows for sure whether Pennington’s shoulder will allow him to play a full season,no one can say whether Curtis Martin will be an effective running back. Martin is 32 years old and recently had knee surgery, so it’s unrealistic to expect him to be an every-down back in 2006. If Martin is with the Jets at all next year, Mangini will probably put him below both Derrick Blaylock and Cedric Houston on the depth chart.

All of the questions about the Jets’ personnel mean that the most important question about Mangini isn’t whether he can run a defense like Belichick. The most important question is whether he and general manager Terry Bradway can acquire personnel like Belichick.

“Being compared to Bill Belichick is one of the highest compliments that you could be paid,” Mangini said. Jets fans just hope Mangini is being compared to Belichick five years from now.

Mr. Smith is a regular writer for FootballOutsiders.com.

HISTORY’S YOUNGEST NFL HEAD COACHES

1. Harland Svare, L.A. Rams 31 years, 11 months
2. John Michelosen, Pittsburgh Steelers 32 years, 2 months
3. David Shula, Cincinnati Bengals 32 years, 7 months
4. John Madden, Oakland Raiders 32 years, 10 months
5. Don Shula, Baltimore Colts 33 years, 4 days
6. Al Davis, Oakland Raiders 33 years, 6 months
7. Joe Collier, Buffalo Bills 33 years, 7 months
8. Bob Snyder, L.A. Rams 33 years, 11 month
9. Jim Trimble, Philadelphia Eagles 34 years, 3 months
10. Jon Gruden, Oakland Raiders 34 years, 5 months
11. Bill Cowher, Pittsburgh Steelers 34 years, 8 months, 13 days
12. Joe Kuharich, Chicago Cardinals 34 years, 8 months, 25 days
13. Norm Van Brocklin, Minn. Vikings 34 years, 10 months
14. Joe Schmidt, Detroit Lions 34 years, 11 months
15. Eric Mangini, New York Jets 34 years 11 months
16. Mike Shanahan, L.A.Raiders 35 years, 6 months