SAN DIEGO — Coach Danny Sprinkle sort of already knew what his Montana State Bobcats would be in for on Friday. But just in case, as Sprinkle made the rounds doing prep work, a Big 12 coach whom he didn’t name made sure to remind him of Texas Tech’s threat: “They’re as real as it gets.”

Defensively, the Red Raiders entered the N.C.A.A. men’s basketball tournament leading the nation in adjusted defensive efficiency at 66.6 points per game, according to Kenpom.com. They ranked sixth nationally by holding opponents to 38.4 percent shooting. They limited Iowa State to 41 points in a conference tournament quarterfinal game, establishing a school record for fewest points allowed against a Big 12 opponent.

They are long and lean, listing four guards in their starting lineup, all between 6-foot-5 and 6-foot-8. They attack in swarms. They are voracious readers of pick-and-pops and move on screens as neatly as a well-choreographed dance line. And they were every bit as real as it gets with a 97-62 blowout of the Bobcats in the round of 64 on Friday.

The Red Raiders’ first-year coach, Mark Adams, 65, is a Texas Tech graduate (1979) and an old-school defensive guru who worked his way up from the N.A.I.A. and community college ranks. He preaches toughness, knits togetherness and worships at the altar of almighty defense.

“This is definitely the most different defense I’ve ever played,” said Bryson Williams, a senior forward who transferred this season from Texas-El Paso after starting his college career at Fresno State.

The Red Raiders work hard to funnel the ball toward the side of the court and then use all five defenders to work to keep it there until they force a turnover, a poor shot or get a stop.

“Coach Adams does a great job of demanding how hard we play at that end of the court, never taking a possession off,” said Sean Sutton, the son of the Hall of Fame coach Eddie Sutton and an executive adviser on the Texas Tech basketball coaching staff. “We get in passing lanes and try to cause havoc, try to get our hands on balls. And with our length and size, we’re able to challenge a lot of things in the paint because of it.”

The Red Raiders completed an emotional, two-game season sweep against Texas on Feb. 19, holding their opponent to just 10 points in the paint in the 61-55 win. Texas Coach Chris Beard had stunned Texas Tech by leaving for the rival Longhorns after last season.

It was Beard who brought Adams to Lubbock, as an assistant for the 2016-17 season. Adams was the defensive architect of Texas Tech’s 2018-19 run to the national championship game — the Red Raiders led the nation in defensive efficiency that season — and he was promoted to head coach this season. Only he and Sutton remain at the school from Beard’s staff.

“That’s the main reason I stayed, to stay with him,” Kevin McCullar, a 6-foot-6 guard, said of Adams. “When we brought in a bunch of new guys and stuff, we all just jelled so easily. We did a lot better than people thought we would do with the coaching changes. We’re not settling. We’re trying to make history.”

To the coach, not much has changed as he moved from the second chair to the first.

“I have always been a defensive coach,” Adams said. “At least, in my mind, even back in junior college. We’ve always been really good on the defensive end. I’ve tweaked it. I’ve stole from everybody. Coach Sutton and Bob Knight. Dick Bennett. All those guys.”

He said his two biggest influences were Sutton and Gerald Myers, the Texas Tech coach from 1971-91 for whom Adams worked as a graduate assistant. Myers introduced him to man-to-man defensive concepts. Adams was in charge of defense in his first season at Texas Tech under Beard, when the Red Raiders went 6-12 and allowed a minus-71 point differential.

“I went back that summer and started looking and trying to study Kansas and Baylor,” Adams said. “And that’s where this evolved.”

The early evolution started with Dean Smith at North Carolina, Knight at Indiana and Henry Iba, who coached Sutton’s father at Oklahoma State in the 1950s. As Sean Sutton explained, many teams “have funneled the ball toward the baseline going back many, many years.”

“But keeping the ball on the side and not letting it get back to the middle,” Sutton said, “I don’t think anybody had ever done that. And that’s what Coach Adams started four or five years ago.”

Playing this style of defense, Sutton said, takes communication. “You can’t have loose switches where guys start slipping,” he said. “So we put a big premium on staying in stances but communicating with each other and coming together on switches and trying to keep the ball on the side, or, for sure, out of the paint.”

This season there wasn’t much margin for error. Only five players returned from last season, and Adams was blending in eight transfers.

“I think it’s difficult for any coach when you bring a transfer in because they’ve got a certain role and they’re the best player on the team, most of them,” Adams said. “And they’re getting the most shots and getting the most touches. And then you bring them in and say: ‘We love you, but we’re doing it a different way. We’re going to share the ball. And we’re going to play defense. If you want to do those things, you’ll get to play a lot of minutes.’”

Adams’s defense is not foolproof, of course. Trouble can arise if the ball reaches the middle of the floor and Texas Tech’s defense is so overloaded with help on one side that an opponent skips a quick pass to the weak side, leaving the Red Raiders in “long close-outs,” Sutton said. Bill Self, the Kansas coach, has been able to crack the code a few times, most recently in the Big 12 title game, a 74-65 Jayhawks victory.

“There’s not many flaws in it, but there are a few areas where you can attack,” Sutton said. “And when something like that happens, Coach calls timeout and tries to get it fixed.”

What rival coaches often do is come calling or visiting in the off-season to pick Adams’s brain. As others did for him, Adams has shared some of his schemes, with N.B.A. personnel and college and high school coaches.

“Probably the best compliment was Baylor’s Scott Drew,” Adams said. “They kind of took their mini-zone and came back and started running our side defense, and he gave me a lot of credit, said I ought to write a book, and they won a national championship. The only problem with that was he started running it better than I did. I was a little jealous of that.”

Of course, those coaches looking to borrow from Adams should be on alert that maybe there isn’t full transparency.

“He doesn’t share everything,” Rick Cooper, Adams’s chief of staff, said, grinning — emphasis on “everything.”