The UConn bench is all smiles celebrating its win Sunday in the NCAA Tourney. (AP photo)

Connecticut romped through the NCAA Tournament’s opening weekend in such fashion that coach Dan Hurley is using one word to describe the reigning national champions’ vulnerability.

“We’re bulletproof,” Hurley said after UConn routed Northwestern in the second round. “Again, elite offense, elite defense.”

For UConn, like the rest of the 16 teams left in March Madness, the underlying data reveals plenty beyond those on-court performances. A chalky bracket with four No. 1 seeds still alive features multiple teams fitting the profile of past Final Four teams and title winners in KenPom’s efficiency metrics.

In data going back to 2001, 15 of 22 national champions ranked inside the top 25 in both offensive and defensive efficiency entering the NCAAs. Four outliers ranked inside the top 10 for offensive efficiency while the other three did so for the defensive side.

And when it comes to Final Four teams, more than half (49 of 88) were top-25 teams on both sides, while 20 of those outliers ranked at least in the top 10 of one category. The other 19 did neither.

That creates three tiers of Sweet 16 teams:

— Seven ranking inside the top 25 on both sides: the Huskies, fellow 1-seeds Houston, Purdue and North Carolina; 2-seeds Arizona and Marquette; and 3-seed Creighton.

— Seven teams that are top-10 performers at one end: 2-seeds Tennessee and Iowa State; 3-seed Illinois; 4-seeds Duke and Alabama; and 5-seeds Gonzaga and San Diego State.

— Two outliers: 6-seed Clemson and 11-seed North Carolina State, part of the Atlantic Coast Conference’s national-best four Sweet 16 teams.

The Huskies’ numbers look just as dominant as their play.

UConn entered the NCAA Tournament ranked No. 1 by averaging 126.6 points per 100 possessions, trailing only 2018 champion Villanova (127.4) and 2015 runner-up Wisconsin (126.8) for the best of any team’s adjusted offensive efficiency since 2001.

The Huskies also ranked 11th defensively coming into March Madness at 94.4 points allowed per 100 possessions, and now they have cracked the top 10 there, too, when factoring in tournament games. Through two NCAA games, the Huskies are averaging 1.29 points per possession and scoring on 59.7% of their possessions; opponents Stetson and Northwestern managed 0.853 and 39.5%, respectively.

“I think the biggest thing that makes you bulletproof in tournaments is if you play elite defense, if you play elite offense,” Hurley said before the Northwestern win. “If you’re a really, really strong rebounding team. If you play really, really hard. If you share the ball. If you’re not reliant on one or two players to carry you.”

Throw in quality game prep and scouting, he said, and “it puts you in a position where you’re not too vulnerable.”

The closest profile to UConn’s for a still-playing team is Arizona, which ranked eighth in offense (121.1) and 12th in defense (94.5) entering Round 1.

“We’re built to play lots of different styles,” Wildcats coach Tommy Lloyd said before a second-round win against Dayton. “And generally, if you want to be a team that’s playing in transition, you better be a good defensive team so you’re not taking the ball out of the net. … And then you want to rebound the ball well.

“You put those things together, good defense and rebounding usually gives you an opportunity to play in transition offense.”

Of the remaining teams in that top tier, Purdue (fourth, 125.0) and Creighton (12th, 120.1) ranked stronger on the offensive side, while Houston (second, 87.2), UNC (sixth, 93.2) and Marquette (19th, 95.6) were better defensively.

Boilermakers coach Matt Painter, whose team has buried the ghost of last year’s Fairleigh Dickinson loss, echoed Lloyd on the value of balance.

“As you get the tournament and you play quality people, you’ve got to be able to steal points somewhere,” he said after Purdue scored 106 points in the second-round win against Utah State. “You can’t just play in the halfcourt.”

As for the second group, Alabama, Illinois, Duke and Gonzaga are all top-10 offenses, while Iowa State (first, 87.1), Tennessee (third, 91.1) and San Diego State (ninth, 93.8) were top-10 defenses.

And in a chalky year, that leaves Clemson (27th offense, 67th defense) and N.C. State (47th offense, 89th defense) as the remaining underdogs.

Then again, N.C. State already has proven that much can change quickly. Kevin Keatts’ club became the first to win five games in five days at the ACC Tournament for the program’s first title since 1987, and now it has extended that with two March wins — the Wolfpack hadn’t won more than four straight games at any point since the 2020-21 season until now — for the program’s first Sweet 16 trip since 2015.

The mantra there has been simple for a team that wouldn’t have made the NCAAs without that ACC run: “Why not us?” And that belief has some value beyond the metrics, too.

“I think that’s what March is about,” nimble big man DJ Burns Jr. said after the second-round overtime win against Oakland. “Some teams got here by winning their conference just like us and that doesn’t mean they’re a bad team. We executed and shoot, we just kept playing for each other.”

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