Elena Delle Donne defends Astou Ndour of Spain at the Rio Olympics in August.  (Andrej Isakovic/Agence France-Presse via Getty Images)

The Washington Mystics have reached an agreement in principle to acquire Elena Delle Donne, the 2015 WNBA MVP, from the Chicago Sky, according to people familiar with the negotiations.

The deal involves Washington sending the Sky the No. 2 overall pick in the 2017 WNBA draft, as well as center Stefanie Dolson and guard Kahleah Copper. Dolson was a first-time all-star in 2015, and the Mystics drafted Copper with the No. 7 pick last year.

Mystics General Manager and Coach Mike Thibault was unavailable to comment, but sources requesting anonymity because the deal is not officially complete indicated on Monday night that the terms are in place for Washington to acquire the 2016 Olympian.

Delle Donne is a restricted free agent, which allows the Sky to match any contract offer, but has said she wants to play closer to her home in Delaware, even suggesting she would be willing to sit out this season to facilitate a trade.

WNBA free agency began on Jan. 15, but deals do not become official until Wednesday, when players are first permitted to sign.

Blockbuster moves are uncommon in the WNBA given league-wide financial limitations, although two years ago center Sylvia Fowles, a three-time Olympic gold medal winner, forced a trade from Chicago to the Minnesota Lynx by sitting out the first half of the season.

The Lynx won the WNBA championship that season for the third time in five years, with Fowles named Finals MVP.

Delle Donne helped Chicago reach the playoffs, including the 2014 WNBA Finals, in each of her four seasons in the league. In 2015, she averaged 23.4 points per game to win the WNBA scoring title in addition to career highs of 95 percent shooting from the free throw line, 8.4 rebounds and 2.0 blocks per game.

This past season, Delle Donne averaged 21.5 points, the second most in the league, before injuring her right thumb in a 118-81 loss to the Mystics on Sept. 7. Shortly thereafter she had season-ending surgery, keeping her out of the final 10 games.

Other injuries that have limited Delle Donne during her career include a concussion and a sore back.

Delle Donne also has sat out lengthy stretches both as a professional and at the University of Delaware because of Lyme disease.

Delle Donne had been in China playing overseas when a recurrence of the disease compelled her to fly back to the United States last week for treatment.

“Lyme disease is difficult to manage many times, especially now,” Delle Donne told the Associated Press during a short news conference. “I’m really struggling with my health right now. For my health, the best thing for me is to return to the U.S.”

Still, the addition of Delle Donne provides the Mystics with the highest-profile player in franchise history since they drafted Chamique Holdsclaw No. 1 overall in 1999. Delle Donne was the No. 2 overall selection in the 2013 draft, when the Mystics picked No. 4 in the first season under Thibault.

Washington selected Tayler Hill after Brittney Griner, Delle Donne and Skylar Diggins were off the board.

The Mystics finished 13-21 this past season with an injury-depleted roster, missing the playoffs for the first time in Thibault’s four years. Washington had lost in the Eastern Conference semifinals in each of the previous three seasons and has not advanced beyond the first round since 2002.

The Sky, according to sources, initially had expressed strong interest in acquiring Emma Meesseman as part of the deal for Delle Donne, but Thibault has been unwilling to part with her. Meesseman, a first-time all-star in 2015, signed a contract extension last year, keeping her off the free agent market.

Washington, meanwhile, may not be done fortifying its roster, according to sources, following a deal announced on Monday afternoon in which the Mystics acquired the No. 6 overall pick in the 2017 draft from the Seattle Storm in a three-way trade that included the New York Liberty.

In a move to clear salary cap space, Washington sent guard Bria Hartley and center Kia Vaughn to the Liberty, which traded center Carolyn Swords to the Storm. The Mystics also exchanged second-round picks with Seattle, moving down to 18th overall from No. 15.