The validity of the call will long be debated on barstools at the Final Four, but Flagg put himself and Duke in a vulnerable position by appearing to hold down Roberts’ left arm and getting whistled for it.

Roberts, a 63% free throw shooter, changed the game by making both ends of the one-and-one, pushing Houston to a 68-67 lead and setting the stage for Flagg’s final foray.

For a program that holds a defiant image of grit and toughness, it’s fitting that Houston’s trip to the national title game featured a game-changing boxout. Kellen Sampson, the Houston assistant and son of Cougars coach Kelvin Sampson, broke out one of his father’s folksy basketball sayings to sum up the moment.

“Discipline gets you beat more than great helps you win,” Kellen Sampson said. “I’ve probably heard it a hundred million times growing up. Look, the more disciplined you are, the more that you can find yourself doing little tiny things that’s going to win.”

“A big-time free throw blockout was exactly what was needed,” he added.

Regardless of any debate over the call, Flagg’s foul put Duke in a suddenly unthinkable position. The Blue Devils went from a six-point lead with 35 seconds left to trailing by one at the 19-second mark. The foul was the final swing: up one to down one.

The key for Houston came from leaving Roberts alone on Flagg, something it didn’t do early in the game. Flagg picked the Cougars apart with his passing, and they made an adjustment to let Roberts handle the matchup by himself.

“We said here at halftime we’re going to trust J’Wan,” Sampson said. “He’s doing a heck of a job in his one-on-ones against Cooper. We’re probably over-helping.

“You have the No. 1 defense in America for a reason. Trust him.”

Houston’s defenders were their marauding selves all night, with the most jarring statistic in the box score being that of Duke center Khaman Maluach when he failed to grab a rebound in more than 21 minutes of play and ending the night with a plus-minus of -20.

Roberts’ final salvo was getting a tough contest on Flagg’s potential game winner.

“I thought he did an awesome job of getting his hands up high enough that it wasn’t an easy look,” Sampson said of Roberts. “Some tough shots all night.”

Flagg finished the contest with 27 points, shooting 8-for-19 from the field. He got little help, as Duke had only one field goal over the game’s last 10:30.

He rode back to the Duke locker room in a golf cart at 11:54 p.m., staring into space with a towel wrapped around his neck. Flagg entered the cone of silence suddenly facing the end of a season and likely a college career.

Three minutes later, Duke coach Jon Scheyer rode past with his wife next to him and athletic director Nina King sitting in the back. After leading by as much as 14, Duke had just coughed up the fifth-biggest lead in Final Four history. The loss will echo, just like that slamming door, long into the offseason.

“I keep going back, we’re up six with under a minute to go,” Scheyer said.

“We just have to finish the deal.”