Friday, in Phoenix, the Lynx thumped the Mercury, winning their sixth straight regular-season game against their conference archrival.

Sunday at Xcel Energy Center, the rematch. Of sorts. Phoenix came north without center Brittney Griner and guard Diana Taurasi. Griner was injured. Taurasi, apparently, needed a rest.

So perhaps the 10,022 fans — the second-biggest home crowd of the season — thought it would be easy.

If so, they were half right.

Down at halftime and even six minutes into the third quarter, the Lynx dropped the hammer, an 18-0 run that turned a game from being way too close to one that was way over.

The 81-66 victory pushed the Lynx to 15-2 at the season’s midpoint, 2½ games ahead of Los Angeles for the best record in the league.

“The game was as we thought it would be,’’ said Lynx coach Cheryl Reeve, conducting her postgame interview with 2½-year-old son Oliver in her lap. “Phoenix is a good defensive team. They’re physical.’’

But without Taurasi and Griner, there wasn’t enough offense.

Still, thanks to a defense that surrounded Lynx center Sylvia Fowles every time she got the ball, and with an offense that shot close to 60 percent in the first half, the Mercury (11-8) was ahead by four at halftime against a Lynx team that couldn’t shoot straight.

At halftime, that changed.

After consulting with the players, Reeve adjusted the defense.

Then the Lynx took over.

Well, eventually.

Camille Little’s jumper with four minutes left in the third put the Mercury up by two. On the ensuing possession Fowles got the ball at the free throw line. She turned around and saw …. nobody.

“I couldn’t believe nobody was guarding me,’’ said Fowles, who had 18 points and surpassed 4,000 for her career. “It was the parting of the Red Sea.’’

Stunned, she hesitated. Then she dribbled down the lane, scored, was fouled and completed the three-point play. After a Phoenix turnover at the other end, Jia Perkins fed Fowles for a layup and the Lynx were off.

Those were the first five points of an 18-0 run that ended with Renee Montgomery’s two free throws with 50.6 seconds left in the quarter. The run also included five points from Fowles, six from Montgomery and five from Plenette Pierson.

Take away that three-plus minutes of dominance by the Lynx, and this was a one-possession game.

But it came down to defense. Phoenix shot 27.8 percent in the second half, making just one of 10 three-pointers, with seven turnovers in the second half. The Lynx, meanwhile, shot nearly 48 percent in the final two quarters, 53 percent in the 29-11 third.

Did the halftime speech hit home?

“She was actually nice,’’ Fowles said. “She just came in here and said, ‘Look ladies, we know what we have to do.’ ’’

Said Maya Moore: “The last thing Cheryl said coming out of the locker room at halftime was, ‘We get this back with our defense.’ That’s what you saw.’’

The Lynx got great bench production, with Perkins scoring 13, Pierson and Montgomery 10. Rebekkah Brunson had 11 points.

The Mercury was led by Yvonne Turner’s 18 points off the bench. Monique Currie had 13 starting for Taurasi and Danielle Robinson had 10.

The score was onesided at the end, but it took a lot of second-half defense for the Lynx to get there.

“We responded,’’ Moore said. “We felt the second quarter got away from us. This team plays off our defense.’’