Head Coach Bill Belichick and the Patriots have built a defensive identity not predicated on one. (NFL Game Rewind)

Head Coach Bill Belichick and the Patriots’ defense have pieced together an identity not predicated on one. (NFL Game Rewind)

Bill Belichick’s defense doesn’t look the same as it did in 2000.

It was then that the first-year New England Patriots head coach assembled a defensive line of nose tackle Chad Eaton, left end Brandon Mitchell and right end Bobby Hamilton, while behind them stood linebackers Willie McGinest, Tedy Bruschi, Chris Slade and Ted Johnson.

Together they filled out a 3-4 front seven on a 5-11 Patriots team. But some of those key components up front would shift in 2001, and so would the results.

Those results began early on, as Belichick and director of player personnel Scott Pioli drafted University of Georgia five-technique named Richard Seymour No. 6 overall, and signed a 6-foot-5, 280-pound right end named Anthony Pleasant, a 33-year-old outside linebacker named Roman Phifer, and a former Pittsburgh Steelers special-teamer named Mike Vrabel to fill out the rest.

The rest helped New England go 11-5 on the way to winning the Super Bowl. The defensive personnel adjustments were integral in the reason why. And those adjustments have continued to evolve in time, as the Patriots have gone from a 3-4 base to a 4-3 base to a hybrid nickel defense without a definitive identity.

In process, they’ve found one.

“I think that’s part of building your team is trying to anticipate where your team is going and to a certain extent where, especially defensively because you have to react to what they put on the field,” Belichick said in his Wednesday press conference. “Defensively you have to be able to defend those things. How do you construct the defense so you can handle the different challenges that you have?”

Those challenges have started within opposing offenses, where bell-cow running backs, blocking tight ends and two-receiver sets are not the prominent features they once were. Two-dimensional rushing committees, receiving tight ends and three-wideout sets have, in many ways, changed the speed in which the game is played.

Defenses have had to counter on the back end with nickel and dime defenses to make up the difference, building a roster as deep in the secondary as in between the tackles.

“I think if you look at the numbers statistically, the amount of five defensive backs that are on the field, you’ll see numbers shift dramatically but particularly this year,” Belichick said. “You can see a trend, but there’s a spike. There’s only a very few number of teams, maybe four or five, that were under 50 percent nickel. So, when you talk about what defensive system do you run – virtually every team in the league, the defense they play the most is nickel.”

New England’s has followed suit. Four Patriots cornerbacks – Darrelle Revis, Brandon Browner, Kyle Arrington and Logan Ryan – all logged at least 450 defensive snaps in 2014. And at times, Belichick and defensive coordinator Matt Patricia have also featured three or four safeties on the field at once.

“I think we’re in the 75 percent range of nickel defense this year. Now you know, we’ve been ahead some, but we’ve also played a lot of multiple receiver teams. That’s flipped a little bit for us too,” Belichick, now in his 40th NFL year, added. “We’ve seen less nickel than a lot of other teams have. We go back to some of our other teams five, six, seven years ago, when we had a lot of three-receiver sets on the field, we saw more nickel than any team in the league.”

The Patriots may be going in the opposite direction of league trends on offense, yet with the expanded number of backs on the field defensively, the number of defensive lineman and linebackers has become a dependent variable.

Whether that has made them a 3-4 or 4-3, a 3-3 or 4-2 remains uncertain. But in a game of trends, New England has found the right ones to piece together a versatile one of their own.

“When we put in the 3-4 in 2000-2001, there were three teams running it. It was us, Pittsburgh and I don’t know where the other team was. So, if you wanted a nose tackle, there were plenty of them out there,” Belichick said. “If you wanted a 3-4 outside linebacker, there were plenty of them out there. Guys like [Rosevelt] Colvin was a good example at Chicago or even [Mike] Vrabel, those 3-4 outside linebackers, but there’s nowhere to go.”

Fellow rush linebackers in Tennessee Titans castoff Akeem Ayers and former New Orleans Saints long snapper Rob Ninkovich have found a place to go. Both have become key features in a Patriots defense not limited to a base, sub-package nickel or dime package.

Colvin and Vrabel once became similar features in the team’s 3-4.

“New England was a good option for both of them because the guys Mike was playing behind and Rosie was trying to play a 4-3 – walked off the line linebacker to a defensive end in sub situations. But it wasn’t really a clean fit for him. So he had a much cleaner fit in the 3-4,” Belichick said of his former players.

Those clean fits have hinged on multiplicity.

The likes of defensive end Chandler Jones, as well as defensive tackles Vince Wilfork, Sealver Siliga, Chris Jones and free-agent acquisition Alan Branch have solidified the rotation. The likes of 2012 and 2013 draft picks Jamie Collins and Dont’a Hightower have solidified the second level. And collectively, their ability to do more than one thing at the line has helped others round out the rest.

Those fits have afforded the Patriots with an adaptable scheme; one that is not restricted to finding one particular type of player to fulfill it.

“You look back five, six years ago and you’ve got 16, 17, 18 teams playing 3-4. You go to the draft board and think, ‘Here’s a nose tackle. Who needs a nose tackle?’ Well eight teams in front of you need a nose tackle and there’s two nose tackles. It’s something you have to figure out where you can get the players to play in your system,” said Belichick.

Getting the right player to fit the system, as Belichick notes, is easier when the system is never final.

“Sometimes you just can’t get them so either you have to change your system or modify it or play with lesser players if you want to maintain system,” Belichick said. “That’s definitely a challenging part of it is keeping up with that, trying to stay at least even with it. Hopefully ahead of it, but at least even.”