The Mystics went 1-3 during the regular season when Elena Delle Donne did not play. (Nick Wass/Associated Press)

As the Washington Mystics wrapped up practice Thursday morning at Smith Center by casually shooting three-pointers, Elena Delle Donne was not with her teammates.

The all-star forward instead was testing her ailing left knee in the nearby pool at the arena where the No. 3 seed Mystics are set to face the second-seeded Atlanta Dream on Friday night in Game 3 of the best-of-five WNBA semifinals.

Delle Donne’s availability for Washington’s first home game of the series will remain in doubt until the 8 p.m. tip-off, according to General Manager-Coach Mike Thibault.

He added that the former WNBA MVP would take part in Friday morning’s shoot-around to gauge the pain level of a bone bruise from Tuesday night’s Game 2 loss.

“She’s tough. If she can play, she will,” Thibault said. “We’ll see. It’s been kind of round-the-clock rehab.”

Extensive testing revealed the deep contusion the morning after Delle Donne’s knee bent awkwardly when she planted her left foot on a drive late in Tuesday’s 78-75 loss that evened the series. She immediately fell to the floor beyond the baseline, clutching her left knee.

Teammates helped carry Delle Donne to the locker room area, where she was able to put some pressure on the joint while lightly jogging.

Still, despite relief throughout the organization that there was no ligament damage, the prognosis for coming back from a bone bruise varies significantly, at least in Thibault’s experience. The WNBA’s all-time winningest coach cited examples of players he has coached who have been able to play after several days’ rest but others sitting out more than a month.

Another high-profile area athlete, Washington Nationals outfielder Bryce Harper, missed 42 games last season with a bone bruise in his left knee resulting from a hyperextension Aug. 12, 2017. His first game back was Sept. 26.

“I think we’re fine,” said Mystics guard Monique Currie, a 12-year WNBA veteran. “We didn’t really talk about her today, actually. We just went through practice as we normally would. Obviously we’re hoping that she’ll be fine for tomorrow, but we know that we have to be prepared for her not to be.”

The contingency plan without Delle Donne includes reserve Tianna Hawkins moving into the starting lineup at power forward.

Hawkins started the four games Delle Donne missed this season because of a recurrence of Lyme disease. Washington went 1-3 without Delle Donne, but Hawkins averaged 12.8 points and 6.8 rebounds during that stretch, which included three road games.

In her time as a starter this year, the former standout at Maryland also made 5 of 11 three-pointers, a part of Hawkins’s game that has improved considerably since she was selected No. 6 overall in the 2013 draft, four slots behind Delle Donne.

Delle Donne is averaging 26 points and 13 rebounds in three postseason games this year. She had 27 points and personal playoff highs of 14 rebounds and six assists in Game 2, helping stake Washington to a double-digit lead it was unable to preserve in the second half at McCamish Pavilion in Atlanta.

The Mystics made just one field goal following Delle Donne’s injury and committed a pair of costly turnovers, including the Dream’s Alex Bentley stealing a pass rookie guard Ariel Atkins intended for Kristi Toliver with 14 seconds remaining. Washington trailed by two at the time.

“It’s a huge relief there’s not ligament damage, but she’s still having some trouble, and she’s still injured,” Hawkins, who played Game 2 with a mild illness, said of Delle Donne. “I think the atmosphere in the locker room is we all want to win, regardless if she’s able to play or if she isn’t.”

Delle Donne’s injury means Game 3 may take place without two of the best players in the world.

The Dream lost guard-forward Angel McCoughtry to torn knee ligaments Aug. 7 during the fourth quarter of a 109-100 win against the Las Vegas Aces. Without the two-time WNBA scoring champion, Atlanta went 4-1 to close the regular season and claim the No. 2 seed, finishing one game ahead of Washington.

“The things you do best, do those,” Thibault said of his message to the team if Delle Donne doesn’t play. “Don’t try to reinvent yourself. You’re not Elena Delle Donne. You’re not going to be those things. Do what you do well, and play great team defense, and trust each other. The trust factor is, hey, we’ve scored a lot of points with different people out there.”