Kristi Toliver, shown during a regular-season game last month, has helped the Mystics reach the WNBA semifinals. (Katherine Frey/The Washington Post)

On Sept. 3, the Washington Mystics were sitting around a solemn locker room at Xcel Energy Center in St. Paul, processing their fourth double-digit loss of the season to the Minnesota Lynx. The loss marked the end of a regular season that featured a decent record but felt underwhelming.

Elena Delle Donne’s arrival in February was supposed to transform the Mystics into the super team of the Eastern Conference. Instead, injuries hobbled Washington, which limped toward the playoffs as the No. 6 seed with a pair of single-elimination games waiting.

When point guard Kristi Toliver spoke in the locker room that night, she might have seemed a little unhinged.

“I want to be back in this building come mid-September,” Toliver said.

What seemed far-fetched at the time became reality Sunday night, when Toliver made a WNBA-record nine three-pointers and scored a franchise playoff-record 32 points to defeat the New York Liberty, 82-68, and earn the Mystics their first appearance in the semifinals since 2002.

Entering a best-of-five series against the top-seeded Lynx that begins Tuesday in Minnesota, the Mystics are playing their best. With Toliver at the helm, they finally look like the team those around the WNBA had pictured at the start of the season. All they needed was time and a leader.

It wasn’t just the injuries that waylaid Washington’s development. It was the timing of the injuries.

Three of the Mystics’ key figures spread their absences out over the season: Emma Meesseman at the beginning, absent for a little more than a month while playing for the Belgian women’s national team in Europe; Tayler Hill toward the middle, after tearing her right anterior cruciate ligament in mid-July; and Delle Donne toward the end, suffering a left thumb injury that required surgery at the beginning of August.

“You had one person out and you start playing a certain way, they come back and somebody else is out,” Coach and General Manager Mike Thibault said. “So we never had a lot of practice days this year with the full roster to get a rhythm to the offense.”

The Mystics, who finally had everyone except Hill at practice before their first playoff game last week, stunned Dallas, 86-76, thanks to a playoff record-setting 52 rebounds and a balanced offense highlighted by 25 points from Delle Donne and 16 points apiece from Toliver and Meesseman . Center Krystal Thomas set a franchise playoff record with 17 rebounds.

On Sunday in New York, the Mystics trailed by 11 points after the first 10 minutes and had made just four field goals.

Toliver didn’t only see her moment, it stared her in the face. It blared from the speakers at Madison Square Garden, where a DJ kept the hostile crowd noisy. Toliver had joined Washington for games like Sunday’s.

“I knew that I needed to be aggressive,” Toliver said, “and just lead the way that I know I’m capable of.”

The 30-year-old grew up in Harrisonburg, Va., and was a standout at Maryland, where she gained fame as a freshman for sinking the three-pointer that sent the 2006 national championship game against Duke into overtime. The Terrapins won, 78-75.

But Toliver spent the bulk of her professional career away from home in Los Angeles, playing alongside the likes of three-time league MVP Candace Parker and 2016 WNBA Finals MVP Nneka Ogwumike. Toliver was the Sparks’ point guard when they won the league title last season, experience that made her, in Thibault’s mind, one of the more valuable free agents on the market this past offseason.

Washington was attractive to Toliver because it presented a challenge.

“I think mainly for me, this is just a different overall experience,” Toliver said. “Being in L.A., I didn’t necessarily have more of the pressure, more of the eyes on me. I had superstars around me. . . . On this stage, I came here to win. I came here to take a team that hasn’t won in a long time and bring that winning culture. I feel like I have a lot of responsibility here. I was ready for something new.”

After a loss in July, Thibault told Toliver to step up, and she scored 29 points to lift Washington to a win in its next game.

From that point, the usually quiet guard gradually became a leading voice in the locker room. She grew loud enough that she volunteered to write the team’s statement after they decided to stand arm in arm with the Sparks during the national anthem in August after a violent weekend in Charlottesville.

Before the playoffs, Thibault asked her to lead by example and set a more serious tone in the locker room and on court.

“It’s my place to do it,” Toliver said. “I know that’s why I’m here and I know I need to use my voice and take it to another level, because that’s what the playoffs do. Could it have been done earlier in the season? Maybe. But I think that’s just part of the growth in learning and understanding one another in a first-year experience together. . . . I think right now we’re kind of peaking at the right time.

“I think it’s going to be really great for our team’s maturity to go against the elite of the elite. I don’t think there’s a better place than Minneapolis to play in the playoffs.”

She would know. Los Angeles won the WNBA title in Minneapolis last year, with Toliver at the helm.

Correction: Due to a reporting error, a previous version of this story incorrectly stated that a game against the Minnesota Lynx was played at the Target Center in Minneapolis. This season, the Lynx have played all home games at the Xcel Energy Center in St. Paul, while the Target Center undergoes renovations.