It began raining three-pointers left and right at Madison Square Garden on Sunday. They washed away the Liberty’s dream of winning the WNBA’s first prize for the first time.

The season is over. Just like that. Again.

Kristi Toliver erupted for nine three-pointers and scored 32 points for the sixth-seeded Washington Mystics, who rallied from an early 14-point deficit and upset the third-seeded Liberty, 82-68, in a single-elimination second-round playoff game.

Elena Delle Donne added 18 points and 10 rebounds. Another factor was Washington’s 14-3 edge on the offensive glass.

So the Mystics move on to the best-of-five semifinals against top-seeded Minnesota — and the Liberty, which closed the regular season with 10 straight wins, moves on to think about what might have been.

For the second straight year, the Liberty tripped over this step after a first-round bye.

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“It’s disappointing that we’re not getting over the hump,” said Tina Charles, who scored 18 points despite playing with a bad back.

So what happened?

Said Charles, “I think Kristi Toliver happened.”

The Liberty led by six at the break, but Toliver erupted for 17 points in the third quarter. The 5-7 guard capped a 23-5 run from the start of the period by nailing a shot from the right side for her fifth three-pointer in five tries during the burst. Washington led 58-46 and built the margin to 20 points in the fourth quarter.

“We rode her wave today,” Delle Donne said. “She was unconscious.”

The Liberty went ahead 29-15 less than two minutes into the second quarter. Then Toliver contributed three three-pointers and a three-point play to power a 14-4 run that cut the deficit to 33-29.

“I didn’t come here to be a passive, tentative player,” said Toliver, who was on the champion Los Angeles Sparks last season and signed with the Mystics in February, shortly after Delle Donne was acquired from Chicago. “I came to dominate, to lead. What better place to do it than Madison Square Garden?”

So it was another one-and-done postseason for the Liberty.

“When a player like that just goes off,” coach Bill Laimbeer said, “that’s what this format is about.”

Notes & quotes: Hurricane Irma hit Marco Island, Florida, where Laimbeer has a house. One of his parents also lives on Marco Island, the other in nearby Naples. He received a text before the game that said they were OK. “My wife said control whatever I can control,” he said. “It’s just bad luck it came right over the top of my house. You have to laugh about it a little bit because otherwise . . . ” He added, “It’s just material stuff.” . . . The Liberty’s Sugar Rodgers was honored as the WNBA’s Sixth Woman of the Year.

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Mercury ousts Sun. Brittney Griner had 26 points and nine rebounds and Diana Taurasi added 23 points as the Phoenix Mercury beat the host Connecticut Sun, 88-83, to reach the semifinals. Phoenix will play second-seeded Los Angeles on Tuesday night in Game 1 of a best-of-five series.