North Carolina Tar Heels forward John Henson and Terrapins center Alex Len, right, collide over a rebound. (John McDonnell/The Washington Post)

Maryland freshman center Alex Len finally flexed the muscle worthy of his 7-foot-1 frame. Senior guard Sean Mosley battled on every play. And sophomore guard Terrell Stoglin had yet another 20-point performance.

But after dominating No. 5 North Carolina for the first 30 minutes, Maryland squandered a nine-point second-half lead and, with it, a chance to topple a ranked opponent for the first time this season. The result was a second consecutive heart-rending defeat, with Maryland falling to North Carolina, 83-74, on Saturday at Comcast Center. The loss came just three days after Maryland’s double-overtime defeat at Miami.

With Saturday’s loss, Maryland ended the first half of the ACC season at 13-9, 3-5, yet to notch a signature victory and having lost five of its last six.

Coach Mark Turgeon had contradictory emotions afterward. He was proud of his team’s moxie in defending North Carolina’s high-scoring offense but was exasperated by the half-hearted rebounding and selfish shot-taking in the final minutes.

“I’ve never had more trouble getting a team to be more physical on box-outs,” said Turgeon, whose team was outrebounded, 46-39. “We’ve worked on it. We talk about it. . . . A lot of it is us just not competing on the glass when we need to compete.”

North Carolina forward Tyler Zeller, right, dunks over Maryland Terrapins center Alex Len. (John McDonnell/The Washington Post)

After taking a 48-39 lead early in the second half, Maryland let North Carolina reclaim the advantage with 9 minutes 10 seconds remaining. The Tar Heels (20-3, 7-1) held their advantage even as Stoglin’s jump shot with 3:29 to play pulled the Terrapins to 70-69.

That’s when Maryland’s shortcomings showed.

The Terrapins let North Carolina’s John Henson and Harrison Barnes grab one offensive rebound after another for second- and third-chance shots. And Stoglin took all five shots down the stretch for Maryland.

He clanged two three-pointers and two jumpers before finally hitting with 12 seconds left.

Turgeon stopped short of criticizing Stoglin directly. The sophomore is, after all, the ACC’s top scorer and the Maryland player who most relishes impossible odds. Instead, the coach spoke yet again about the need for Stoglin to “trust his teammates more.”

“That’s the only way you’re going to beat great teams,” said Turgeon, a former point guard well versed in the art of distributing the ball. “He has got to trust his teammates.”

North Carolina finished with 20 assists on 31 baskets (point guard Kendall Marshall accounted for 16 of those assists, setting a Comcast Center record). Maryland had just seven assists on 25 baskets.

Terps Coach Mark Turgeon, left, shouts for his team to get down court as the North Carolina Tar Heels defeat the University of Maryland Terrapins. (John McDonnell/The Washington Post)

North Carolina’s Tyler Zeller had a game-high 22 points. Barnes added 18 and Henson had 17.

Len had one of his better games of the season, coming off the bench for 12 points, nine rebounds and four blocks in 26 minutes.

It was a physical game, with both teams saddled with foul trouble early in the second half. And Maryland’s fans set a hostile tone at the outset, booing the pregame reminder about sportsmanship and, in the case of one man in the student section, shouting an obscenity during a solemn pause in the national anthem.

It was the first time Turgeon had coached against his mentor, Roy Williams. And while they shook hands warmly before tip-off, Turgeon didn’t hide his displeasure at game’s end over Henson’s showboating dunk with one second remaining, the outcome already settled.

Until Len was inserted, the opening minutes were an all-Zeller show, with the 7-footer hitting three shots in succession. Freshman Nick Faust (11 points) pulled the Terrapins even at 15 and slashed to the basket for a 25-22 Maryland lead that sent the capacity crowd into delirium.

Len got a putback just before the buzzer to give Maryland a 40-37 halftime lead. North Carolina led only 3:10 of the period.

Afterward, it was difficult for Mosley to find encouragement in another defeat.

“I can say we’re getting better and better and better,” Mosley said, “but we’re not winning, and that’s the most important thing right now: getting a win.”