Mark Turgeon has been a head coach for the past 18 seasons, guided three different schools to the NCAA tournament and garnered four conference coach of the year awards.

But throughout all those successful years, Turgeon can’t recall many defensive performances from his team that compared with what the Terrapins men’s basketball team turned in Tuesday.

With the Terps offense sputtering against Northwestern’s matchup zone — the Terps had a season-low point total despite playing overtime — Turgeon’s squad leaned on a stifling defense in its 62-56 win at Xfinity Center.

While the No. 7 Terps struggled to finish possessions with rebounds and Northwestern turned 16 offensive boards into 16 second-chance points, the Wildcats tied a season-low with 56 points. Plus, the Terps held Northwestern to 34.8 percent shooting from the field, more than 11 percentage points below its season average.

“Defensively, that may be the best effort one of my teams has ever done,” Turgeon said. “They’re hard to guard. They space you.”

Northwestern attempted 18 more field goals than the Terps. But despite the clear advantage in shots, the Terps held the seventh highest scoring offense in the Big Ten in check. After shooting 40 percent in the first half, the Wildcats shot 30.6 percent over the final 25 minutes, including going 1-for-10 on 3-pointers.

The Terps’ solid defense helped them overcome one of their worst offensive performances of the season. They scored 48 points in regulation, 15 below their previous season low, and just 17 in the second half. In the final 4:43 minutes of regulation, the Terps didn’t tally a point.

But the Terps were able to stay in the game by holding the Wildcats to one point in the final 5:34 despite allowing three offensive rebounds on one possession. That defense pushed the game into overtime where the offense came alive with 14 points in five minutes to secure the win.

“It was really hard to score against them,” Northwestern coach Chris Collins said. “From my point of view, I thought it was Maryland’s defense that made it hard on us.”

The Terps’ first line of defense starts with guards Melo Trimble and Rasheed Sulaimon, who’s developed a reputation as a top-level defender. When the Wildcats got past those stars, they had to deal with the Terps’ size. Even without forward Michal Cekovsky (illness), the Terps played four players 6-foot-9 or taller. That length affected the Wildcats’ guards, Bryant McIntosh and Tre Demps.

The duo, which entered averaging a combined 30.2 points per game as Northwestern’s top two scorers, finished a combined 8-for-32 for 18 points.

“When you get past [their guards], they are so big,” Demps said. “They have NBA-type size down there. Once you get past one guy, you have another seven-footer flying at you.”

Northwestern center Dererk Pardon was his team’s most efficient scorer. The freshman had 11 points on 5-for-6 shooting in 15 minutes. But he was plagued by foul trouble in the first half and was pulled for defensive purposes in the second half.

While the Terps’ defensive rebounding struggles nearly proved costly, forward Robert Carter Jr. hauled in a game-high 14 boards to help his team overcome the issue.

After the win, Carter reflected on the Terps defense, like his coach had done minutes earlier. While Carter’s praise wasn’t as effusive as Turgeon’s, he saw something special from the Terps on Tuesday.

“We guarded as well as we have all season at times during the game,” Carter said. “We went over their stuff a lot and scouted them hard, and we knew a lot of that was coming.”