BALTIMORE — At halftime of his team’s NCAA men’s lacrosse semifinal against Duke on Saturday night, Maryland Coach John Tillman asked his defensemen to grade their performance. Duke had scored on its opening shot, after all, and one of the starters gave himself a “D.”

Yet at the time, the Blue Devils had only scored two goals.

Maryland’s defense continued its strong play in the second half — good grades or not — in a 9-4 victory before 45,039 at M&T Bank Stadium in Baltimore.

The Terrapins (13-4) are one win from their first national championship since 1975. In the title game, they will face Virginia (12-5) on Monday at 3:30 p.m.

Fifth-seeded Duke (14-6) scored 54 seconds into the game, but for the rest of the night it went 3 for 27, only shooting 11 percent.

A crucial point came soon after Duke’s opening goal. Maryland’s offense struggled to get its footing in the early going and did not take a shot in the opening eight minutes.

When it finally did manage a shot, the score still was 1-0. Duke had five shots after its opening score; two went wide and three were saved by redshirt freshman goalie Niko Amato.

“They had some really good looks,” Tillman said of Duke. “So it wasn’t just always great defense. . . . We weren’t playing well in certain aspects, but Niko stepped up. Let’s not ask Niko to carry us the rest of the way. Let’s play faster, bear down, communicate better.”

By the middle of the first quarter, one other trend had emerged. The crowd was mostly Maryland fans. And the Virginia fans who stayed must have been mindful that their team has lost 11 of its past 12 against Duke dating from 2004.

So it was a combination of people rooting for Maryland and against Duke. And if the large crowd needed a reason to make noise, it received it three minutes into the game.

As Duke tried to clear the ball near midfield, Maryland sophomore Landon Carr and senior Max Schmidt each registered a huge hit on a Duke player; both times, the Duke player fell to the ground.

The hits also happened within a few feet of the Maryland bench. The bench, and the crowd of pro-Maryland/anti-Duke fans, roared their approval.

“Maryland was too physical, too strong, too athletic today,” Duke Coach John Danowski said. “And I think it showed.”

The Blue Devils have no shortage of physical players either — three of their players also are on the football team.

Yet when sophomore Greg DeLuca, a special teams player who played on kickoff coverage against Maryland in the fall, was going for a loose ball in the second half, he was knocked to the ground by Maryland sophomore longstick midfielder Jesse Bernhardt.

“Jesse is one of the toughest guys in Division I,” Maryland senior attackman Ryan Young said. “We’ll take him in a matchup against anyone.”

Regardless of the physical play, being the crowd favorite and having a goalie with a hot hand, Maryland still needed to score goals to win. Late in the third quarter, a physical play from senior Dan Burns energized the crowd and led to a fast-break goal by senior Grant Catalino that gave Maryland a 6-3 lead.

The Maryland players on the sideline went so wild that Tillman quickly turned around and put his arms in the air, asking for calm. The noise from the crowd, however, continued unabated.

“I’ve never played in front of anything like it,” Burns said. “After each goal, it was electric.”

Catalino finished with three goals on three shots, junior Joe Cummings added two goals and Amato had 13 saves for Maryland. Four players had one goal each for Duke.

Duke won the NCAA title in this stadium last year. The catalyst was C.J. Costabile, who scored the winning goal in overtime of the title game against Notre Dame after he won the faceoff and raced to the goal.

Yet Costabile entered Saturday with a broken hand. He did play defense but took only one faceoff. He lost.

Maryland senior Mark White is out for the year with a knee injury. Yet he does have a role — he carries the state flag onto the field before games. After the game last night, as his teammates streamed onto the field and hugged Amato, White did not join them until he had grabbed the flag first.

On Monday, there is little question about which way the crowd will be leaning.