FOXBORO — As he and trusted adviser Ernie Adams began talking about Pittsburgh in recent days, Patriots head coach Bill Belichick and Adams inevitably spoke of the Steelers’ defense. It has been a strength of the club for years, and for years it has used the same 3-4 scheme.

That got the pair wondering: how long has it been?

So the men broke out their scouting reports from their days together in Cleveland more than 15 years ago.

“We go back to our notes, and yes, it’s the same thing,” Belichick said yesterday. “It’s the same blitzes … I don’t want to say there are no changes, but they are minor. In this day and age, that is pretty rare.”

Rare, indeed. Belichick was asked if he ever delves into his files to see past patterns of other opponents, but he joked that other teams have changed “eight times” since 1991, when Belichick took over as head coach of the Browns and faced the Steelers twice a year.

Though Belichick wasn’t totally serious, he might not have been too far off — New England’s AFC East rivals in Miami and New York have each had seven different head coaches since Belichick left Cleveland in 1995, and the Browns, since being reborn in 1999 after Art Modell moved the franchise to Baltimore, have had four different men in charge.

But the uniqueness of Pittsburgh’s defense isn’t just the length of time that the same system has been in place — it’s that it has largely been successful for all of those years.

This season, the Steelers rank first in the NFL in passing defense and rushing defense and, therefore, total defense, having not allowed a single opponent to total 300 yards of offense in 11 tries, a remarkable feat.

In much the same way that the Patriots have become renowned for their ability to plug a player into a hole and continue on, the Pittsburgh defense has done much the same thing. Outside linebacker Joey Porter leaves for Miami, and James Harrison becomes a Pro Bowl selection at the position. Before Porter, it was Jason Gildon, and before him, Greg Lloyd.

The names change but the results remain the same.

And because the system doesn’t change, Pittsburgh’s scouts know every year what type of player they are looking for to come in, learn at the knee of the current starters and then step right in when their time comes.

It also means that the veteran players can refine, rather than spending time learning new plays or calls, leading to better execution.

“It is probably as veteran as any team you are going to get,” Belichick said. “They have been doing it in that system for a long time. They are very consistent, so I think that helps the drafting and the player-acquisition process. It helps the execution from the guys who are doing it, doing it repetitively, and doing it with the same people.

“You want to keep your offensive line together [to foster communication] and see the game through one set of eyes. Defensively, you like to do the same thing with your front seven and your secondary.”

New England linebacker Mike Vrabel, who spent the first four years of his career with the Steelers before joining the Patriots in 2001, said the tapes Belichick showed him this week looked awfully familiar: they were the same plays that he was running when he was in Pittsburgh.

But with Vrabel on the same team for eight years, learning a system Belichick has had in place for nine years — though New England does change up its game plan every week and adds some new wrinkles on occasion — he knows firsthand how it can be helpful to a player to have one playbook.

“You hear a lot of guys talk about ‘this is my third offensive coordinator, this is my third defensive coordinator in four or five years,’ ” Vrabel said. “I think you get better at what you know and what you do routinely. Certainly, there’s going to be problems and there’s going to be mistakes that you make, but it’s not a glaring problem where you have to start all over. It’s, ‘Hey, you played this wrong, let’s try to correct this.’ We pretty much know what we’re going to get from a year-to-year standpoint.”

So there won’t be anything new for Pittsburgh to throw at the Pats on Sunday. The problem is stopping something they know is coming.

smanza@projo.com