Elena Delle Donne scored 24 points in her debut for the Mystics, who rolled past the Stars, 89-74, on Sunday afternoon. (Toni L. Sandys/The Washington Post)

Elena Delle Donne didn’t get much sleep the night before her debut with the Washington Mystics, her nerves a bit frayed. She did not know what to expect in her first regular season game since coming to the District in a blockbuster offseason deal.

So restless was Delle Donne, the 2015 WNBA MVP, that she reported to Verizon Center more than three hours before Sunday’s tip-off against the San Antonio Stars. Even after a standing ovation during player introductions, Delle Donne, by her own admission, couldn’t fully shake the jitters.

Then she collected a pass from guard Tayler Hill and swished a jumper from the left wing 28 seconds into the first quarter. After that, Delle Donne finally began to settle down, and she went on to score a team-high 24 points to spark an 89-74 win.

“Thank God,” Delle Donne said about making her first shot. “I was like, ‘Okay, I can breathe.’ Coach [Mike Thibault] drew up a play. Tayler hit me on a pop. Thank God that ball went in. I was able to breathe and go from there.”

Said Thibault: “Obviously you come in and get 24 points in your debut, that probably sets a pretty good tone for things.”

Delle Donne made 8 of 12 field goal attempts in one of the more efficient shooting performances of her career. She has never been a high-percentage shooter, though she is trending up. She made 45.4 percent from the field over her first four years in the league, with a career high of 48.3 percent last season with the Chicago Sky.

Thibault aims to change that, with a wealth of three-point shooters around her, forcing opponents to guard beyond the arc, thus allowing Delle Donne cleaner looks at the basket.

With the paint less cluttered, Delle Donne got to the foul line nine times and made eight of the attempts. She is among the most accurate free throw shooters in WNBA history at 93.8 percent. She once made 58 foul shots in a row and these days generates gasps of disbelief in the rare instances when she misfires from the line.

“It was a great first win,” Delle Donne said. “Great to get that one under our belts. I felt we had great chemistry for Day One. The biggest thing I noticed was when our defense was getting stops, we were really able to pick up our pace and play really well. Just got to keep drilling our defense.”

Delle Donne missed all three of her three-point attempts, another unusual circumstance for one of the league’s most dependable shooters from beyond the arc. She finished third in the WNBA last year in three-point field goal percentage (42.6).

The Mystics went 6 for 19 (31.6 percent) on three-pointers, but Thibault said he expects that percentage to increase as players become more comfortable with the offense. Washington has three of the top four three-point shooters from last year in terms of percentage, including forward Emma Meesseman, who led the league in that category.

Meesseman had 13 points, nine rebounds and five assists only days after arriving in the nation’s capital from her native Belgium. Meesseman, an all-star in 2015, had practiced just twice leading up to the opener, and she’s scheduled to play only three more games before going back overseas for world championship qualifying with her national team.

“It felt good even though this was only the third day we’re complete,” Meesseman said, referring to a roster depleted during training camp because of international obligations and minor ailments. “It wasn’t perfect, but to be able to show this already, it’s a good start to the season. Knowing that we can do way better than today gives us good hope for the rest of the season.”

Meesseman, Delle Donne and starting small forward Tierra Ruffin-Pratt (eight points, eight rebounds) were part of a frontcourt that commanded the interior. Washington owned a 39-23 margin in rebounding, 34-20 in points in the point and 21-6 in second-chance points against the Stars, who were led by Monique Currie with a game-high 31 points.

The backcourt also joined in, with starting point guard Kristi Toliver finishing with eight points, two rebounds and four assists in her Mystics debut. Toliver signed as a free agent only days after Delle Donne, leaving the Los Angeles Sparks following a WNBA championship last year.

Toliver, who won an NCAA title with Maryland in 2006, had been playing overseas on the same Russian Premier League club as Meesseman and practiced for the first time Wednesday with Washington.

“It’s different, even just today not knowing the warmup, just little things like that,” said Toliver, an all-star in 2013. “As we continue to play with one another and have these games, it’ll just feel more comfortable. But it’s always comfortable being in the DMV. It always feels like home.”