Second-leading scorer Tayler Hill, out for the season with a knee injury, is one of the Mystics’ missing pieces. (Toni L. Sandys/The Washington Post)

While the Washington Mystics practiced Wednesday afternoon, sitting on the training table off to the corner was injured guard Natasha Cloud. Next to her on a chair was injured guard Tayler Hill.

Absent completely from the auxiliary court at Verizon Center was all-star forward Elena Delle Donne, who had boarded a plane to Los Angeles, where she will undergo surgery to repair her damaged left thumb.

“I hope some of our other players make a lot of shots,” Coach Mike Thibault said with a chuckle. “You know, that’s a lot of points out of the lineup.”

An average of 36.9 points to be exact, representing more than 45 percent of Washington’s per-game output this season. Such is the state of the Mystics with 10 games left in the regular season and a top-four seed in the WNBA playoffs on the line.

Washington (14-10) enters Sunday’s game against the visiting Phoenix Mercury clinging to the No. 4 seed. The Mercury (13-11) is one game back but would claim the tiebreaker with a victory, having defeated the Mystics, 88-80, in the teams’ first meeting July 5.

The top four seeds, regardless of conference, receive a bye into the second round after the league overhauled its playoff format last season.

“They’re huge pieces to what we do, but no excuses,” Mystics point guard Kristi Toliver said of the injuries. “We’re still after getting a lot of these victories this upcoming week. We’re at home a lot, so that’s good for us. We’ve just got to find a way.”

The Mystics head into a four-game homestand, their longest this season, following a 76-74 road loss to the last-place San Antonio Stars on Friday night. Washington had a chance to take the lead or tie twice in the final 10 seconds but missed consecutive attempts in the painted area, underscoring the impact of not having Delle Donne and Hill in particular.

Delle Donne leads the Mystics in scoring (18.8) and ranks seventh in the WNBA. Hill, out for the year with a torn anterior cruciate ligament in her right knee, is third on the team in scoring (13.3) .

The prognosis for Delle Donne was to reenter the lineup perhaps two to three weeks following surgery, meaning the most optimistic timetable would be the final game of this homestand Aug. 18 . More realistically, the 2015 WNBA MVP will be back for the final two weeks of the regular season.

Delle Donne injured the thumb on her non-shooting hand during the first quarter of a 77-70 win at the Atlanta Dream on July 30. It was only her second game back after sitting out three straight plus the All-Star Game in Seattle with a sprained right ankle.

An injury to Delle Donne’s right thumb last year ended her season with six games to go. This time, she is scheduled to have her cast removed in roughly 10 days and then wear a splint during which time she may begin testing how much contact her hand is able to withstand.

Cloud, meanwhile, is out for at least Sunday’s game, her fourth in a row, because of a partially torn plantar fascia in her right foot.

“Obviously, it’s unfortunate with all the injuries we have,” Emma Meesseman said. “We just had Elena back, and they keep coming, but we know we can’t keep thinking about it. We can’t say that, ‘Oh, the season’s lost. We’re going to lose games.’ So we have to fight, and that’s what we’re going to do.”

The Mercury also has been shorthanded recently, with Brittney Griner missing the last six games. The all-star center is nursing a bone bruise in her left knee and a right ankle sprain after landing awkwardly during an 88-71 loss to the Minnesota Lynx on July 14.

Griner leads the league in scoring (22.3) and blocks (2.5) and ranks third in field goal percentage (57.7) and eighth in rebounding (8.2).

The Mercury is coming off a 93-92 loss Friday to the Connecticut Sun, which holds the No. 3 seed. WNBA career scoring leader Diana Taurasi led Phoenix with a game-high 33 points on 12-for-18 shooting.

“Game-planning is certainly different,” Thibault said. “When you game-plan for Griner, that causes so many other problems besides her. It causes issues on how you defend other people because you have to pay attention to her. Now it’s a little bit more of a perimeter game for them. Certainly you start with Taurasi.”