RENTON – The questions directed at coach Pete Carroll last Friday had a similar feel.

What has changed about Earl Thomas? Has Bobby Wagner been playing his best football down the stretch? What’s allowed Byron Maxwell to progress the way he has?

Finally, after the third or fourth one, Carroll decided to address what the questions were really getting at.

“I think we’re asking questions about the same kind of growth and development from our guys,” he said. “These guys have been with us, and they have been through it and they’re just maturing. They’re just growing up.”

It recalled a moment earlier this season. Safety Earl Thomas had just helped the Seahawks hold New Orleans quarterback Drew Brees to 147 yards, his lowest total in seven years. As Thomas described how the Seahawks shut down one of the league’s best quarterbacks on “Monday Night Football,” he remembered his rookie season four years ago. Brees took advantage of his inexperience and picked apart Seattle’s defense.

“I was a boy then,” Thomas said, “but I’m a grown man now.”

The Seahawks are still one of the league’s youngest teams, but they are also a proven, game-tested group. Thomas has started for four years. Richard Sherman and Kam Chancellor have started for parts of three seasons. Wagner has started for two full seasons.

And it is through this experience that a talented defense became one of the most dominant defenses the league has seen in years.

CARROLL ALWAYS WANTED to build Cornerback U. He wanted USC to be known as the place where good cornerbacks came to thrive, and in turn that would sharpen his defenses.

“This system is always really corner-oriented,” Carroll said last year. “In college, I always wanted to be ‘Corner U’ because when you can have the ability to do the things we do with those corners, it allows us to do a lot of other things defensively.”

That never happened. Of all the success Carroll has had in the past 15 years, he never developed top-flight cornerbacks in college.

Of the 44 USC players currently on NFL rosters, only two are cornerbacks. In fact, of the 80 USC players drafted from the time Carroll took over in 2001, only six were cornerbacks. None of the six went in the first round.

Fast forward to the Seahawks training camp this year. Seattle had six cornerbacks — six — who would go on to start a game and intercept a pass this season.

Carroll and general manager John Schneider cut veteran corner Antoine Winfield, considered one of the league’s best slot corners, because Walter Thurmond outplayed him in the preseason. When Brandon Browner was suspended for a year, the Seahawks had no problem replacing him with Thurmond. When Thurmond was suspended for four games, his replacement, Maxwell, played so well that he hasn’t relinquished the starting job.

Ron Parker was cut but started a game for the Chiefs and had two interceptions. Will Blackmon was also cut but started eight games for the Jaguars and had an interception.

In other words, the Seahawks have become the NFL’s version of Cornerback U. Two things helped make that happen.

First, Schneider and his scouts had a knack for finding bigger cornerbacks in the later rounds. Sherman is a fifth-round pick, Maxwell is a sixth-rounder, Thurmond was taken in the fourth round and Browner was signed from the Canadian Football League. None of the five corners on Seattle’s roster were taken higher than the fourth round.

Second, the Seahawks played them early and were patient enough to let them grow. But if last year proved anything, it’s that a good secondary still needs a good pass rush.

MEMBERS OF THE SECONDARY pride themselves on shutting down opposing passing games, but they also understand they need help to do so.

The Seahawks had a decent but unremarkable pass rush a year ago and ended up losing in the playoffs partly because of it. When the time came to really get pressure in Atlanta, Seattle’s defensive front couldn’t do it.

Determined to never let that happen again, Schneider and Carroll set out to upgrade the pass rush. Priority No. 1, they called it. That’s why they added defensive linemen Cliff Avril and Michael Bennett.

Bennett gave Seattle versatility up front; he could be used in a number of situations and a number of different matchups. Avril gave Seattle a proven pass rusher with a history of forcing fumbles.

Schneider said the Broncos’ teams that won back-to-back Super Bowls in the late ’90s had a defensive line that played eight guys in a rotation.

“That’s kind of what we were shooting for,” Schneider said.

The Seahawks were one of the league’s best teams at generating pressure and finished eighth with 44 sacks. More important, they could generate the kind of pressure that would make an already good secondary even better.

“This D-Line is scary, man,’’ Thomas said earlier this season. “I think they’re right up there with us in the back end. They’re just as good as we are.”

The result has been the best defense in the league.

Jayson Jenks: 206-464-8277 or jjenks@seattletimes.com