NEW YORK — DeWanna Bonner and the Connecticut Sun put forth a stellar defensive effort to take the opener of their semifinal playoff series against the New York Liberty.

Bonner scored 20 points, Rebecca Allen added 18 and the Sun held New York to a season low for points in a 78-63 victory Sunday.

“They are such an offensive juggernaut, we had to make things as difficult as possible and I think our team took ownership of that today,” Connecticut coach Stephanie White said.

Game 2 of the best-of-five series is Tuesday night in New York.

Third-seeded Connecticut lost all four games between the teams in the regular season, including getting blown out twice in New York, but that didn’t matter to the Sun.

“It’s 0-0 when it comes to playoffs. We didn’t think about the regular season,” Bonner said. “It’s a new season.”

New York led by three at halftime before Connecticut went on a 16-2 run to start the third quarter. The Sun scored the first nine points during the spurt and Natisha Hiedeman hit two 3-pointers.

The Liberty got within 53-48, but Allen — who was traded from the Liberty in the offseason to the Sun as part of the Jonquel Jones deal — hit her fourth 3-pointer of the game.

Bonner made a pull-up jumper just before the end of the third quarter to extend Connecticut’s lead back to 10. She scored the first five points of the fourth to push it to 70-55 — the team’s biggest lead of the game to that point.

New York, which was led by Breanna Stewart’s 19 points, couldn’t get within single digits the rest of the way.

“They were being aggressive. I don’t think we handled it well, we didn’t stay poised and composed,” Stewart said. “Frustrating to drop this one at home. We’ll bounce back Tuesday.”

Stewart had a rough game, going 7 for 25 from the field, including missing all eight of her 3-point attempts. Jones had 14 points and 12 rebounds for New York — the 15th time that she’s had a double-double this season but the first time the Liberty lost in one of those efforts.

New York, which averaged 89.2 points during the regular season, struggled with no fastbreak points and shot 34% from the field. The Liberty were outrebounded 35-30.

“That was the worst game of the season,” coach Sandy Brondello said. “We have great players and we’ll respond.”

The Liberty advanced to the semifinals after sweeping Washington in a hard-fought first-round series, taking the clincher in overtime. Connecticut made it to its fifth straight semifinals by topping Minnesota in three games.

Connecticut got off to a hot start and led by nine before New York rallied and took a 40-37 lead at the half. Jones had 10 points and Sabrina Ionescu nine for the Liberty. Allen had 12 to lead Connecticut while Alyssa Thomas had six points, five rebounds and five assists.

Thomas finished the game with eight points, 10 assists and seven rebounds.