Wall (27 years, 216 days) became the third-youngest player in NBA history to reach 5,000 career assists, behind Magic Johnson and Isiah Thomas. Wall finished the contest with 5,003 while playing well in his fourth game since returning from knee surgery.

"Every game, I am getting better and better, just trying to get my conditioning up," Wall said in a postgame interview on TNT. "I was able to knock down some shots that I probably wouldn't have made a week or two ago."

Bradley Beal tallied 19 points and Markieff Morris added 13 for the Wizards, who won for just the third time in their past 10 contests. Mike Scott scored 12 points off the bench.

Jaylen Brown made six 3-pointers while scoring 27 points for the Celtics. Jayson Tatum had 12 points and Al Horford contributed 10 points and 14 rebounds.

The victory leaves Washington (43-38) tied for seventh place in the Eastern Conference with the Miami Heat (43-38) entering the final day of the season. Both teams trail the Milwaukee Bucks (44-37) by a game. The Wizards would move up to the No. 6 seed if they win at Orlando and both Miami and Milwaukee lose. A loss to the Magic would assure Washington of eighth place.

Boston (54-27) is entrenched as the No. 2 seed despite losing for the fourth time in the past five games.

Washington forward Otto Porter Jr. scored 12 first-half points before missing the second half with a strained right lower leg. Wizards coach Scott Brooks said "his calf tightened up," during an interview with TNT after the third quarter.

The Wizards trailed by two points at halftime before meandering their way to a 65-59 advantage on Wall's 3-pointer with 6:47 left. The Celtics later were within five on a 3-pointer by Tatum with 1:03 remaining before Scott's basket with 1.5 seconds left gave the Wizards a 79-72 lead entering into the final stanza.

Washington's lead was 84-72 after Beal made three free throws with 10:42 remaining. Beal converted a four-point play to make it 88-74 with 8:57 left.

Wall and Kelly Oubre Jr. connected on back-to-back 3-pointers to give the Wizards a 102-85 lead with 3:01 left to all but seal it.

Brown made five 3-pointers and scored a career-high 21 points in the opening quarter as Boston led by as many as 11 points before settling for a 30-22 lead.

Washington dominated the first 6 1/2 minutes of the second quarter and took a 40-39 edge on Wall's 3-pointer with 5:24 remaining. Boston rattled off the next eight points to take a seven-point advantage and led 54-52 at the break.

--Field Level Media