PROVO, Utah -- When St. Mary's imposes its will on defense, there's few teams in the nation that can stand toe-to-toe with the Gaels. Now that St. Mary's is seeing progress on the offensive side of things, it could add up to the no. 22 Gaels busting more than a few brackets in March.

St. Mary's had no trouble caging BYU's offense over the better part of 40 minutes in a 70-57 victory over the Cougars on Saturday night.

BYU shot just 39.7 percent from the field and went 4 of 14 from 3-point range.

Even when St. Mary's endured a cold spell on offense over the final few minutes of regulation, the Cougars could do little to actually threaten the Gaels in that stretch.

"We didn't turn the ball over and we shot the ball well," St. Mary's coach Randy Bennett said. "We were able to get some separation and it made it tough on them. I think we just kind of wore them out after that."

Calvin Hermanson scored 17 points and Evan Fitzner added 15 to lead the Gaels. For St. Mary's (24-3, 14-2 WCC), it marked the team's first win in Provo since the 2012-13 season.

Bennett had special praise for Fitzner, who scored a new season-high against the Cougars. Fitzner stepped up to the plate with leading scorer Jock Landale battling foul trouble in both halves and picked apart BYU's defense exactly how Bennett hoped.

"We're a little bit different team with Fitzner out there," Bennett said. "He spaces the floor and Dane (Pineau) can play the five. We just play a little bit different out there with Fiztner vs Jock, but it's nice to have a Plan A and a Plan B."

The Gaels entered the game ranked second nationally in scoring defense, allowing just 56.3 points per game.

BYU (19-10, 10-6 WCC) struggled to figure out how to threaten that defense for more than short bursts here and there. The Cougars trailed over the final 34 minutes of regulation after struggling to find any consistent offensive rhythm.

"It seemed like we shot it when we should pass it and we passed it when we should shoot it," BYU coach Dave Rose said. "It got us into a lot of awkward situations and then we kind of got on our heels and were afraid to actually attack and then they took advantage."

Mika scored 18 points, Yoeli Childs added 13 and T.J. Haws chipped in 11 to lead BYU.

Once Saint Mary's took control before halftime, the Gaels kept the gas pedal pressed to the floor in the second half.

BYU went nearly 6 1/2 minutes without a field goal at one point before Haws broke the ice with a jumper. It allowed Saint Mary's to string together a 14-2 run to put the game out of reach.

Hermanson and Fitzner helped fuel the run with two baskets apiece. Joe Rahon capped it with two free throws, giving the Gaels a 62-40 lead with 9:31 remaining.

Saint Mary's led by as many as 25 points after halftime. The Gaels carved out a 69-44 lead on a Fitzner 3-pointer with 7:25 left.

BYU held Saint Mary's without a field goal over the final seven minutes, but could only manage 13 points during that closing stretch.

"That team made a lot of runs on us," Haws said. "Tough defensive and offensive team. Very poised and disciplined. I want our team to just fight. When they punch us in the face, I want us to punch them right back."

Saint Mary's used a combination of efficient shooting and stifling defense to create a safe distance between it and BYU early in the first half.

After the Cougars took a 12-11 lead on a 3-point play from Eric Mika, the Gaels gradually pulled away by attacking from the perimeter. Tanner Krebs and Hermanson each buried a 3-pointer as part of a 10-3 run that gave Saint Mary's a 26-18 lead.

BYU cut it to a three-point deficit on a 3-pointer from Elijah Bryant. Hermanson immediately answered on the other end and Jordan Hunter added a layup on the next possession to preserve Saint Mary's lead.

Hunter extended the lead for the Gaels to 36-26 with 2:49 left before halftime on a jumper, capping another 10-3 spurt.

St. Mary's shot 57 percent from the field in the first half, a key reason BYU stayed a step behind once it fell behind the Gaels.

"Our defense has saved us all year, but our offense is starting to come around," Bennett said.

NOTES: Saint Mary's has finished second or higher in the WCC in eight of the last nine seasons. The Gaels have won 25 or more games eight times in the past 12 seasons. ... BYU F Eric Mika has scored in double figures in all 29 games he has played this season. ... Saint Mary's C Jock Landale ranks in the Top 25 nationally with 12 double-doubles this season. He has scored in double figures in 25 of 27 games this year. ... BYU has won at least 20 games and reached the postseason 11 straight years. Both streaks are a program record.