John Wall and Bradley Beal will soon experience playoff basketball for the first time in their professional careers. (Alex Brandon/Associated Press)

Towel draped over his shoulder, John Wall didn’t have any worries as he sat for the entire fourth quarter of the Washington Wizards118-92 victory over the Boston Celtics, gleefully letting the deep end of the bench close out a game that will take him — and the franchise he was drafted to lead — to a place he has never been. A long, painful and often embarrassing wait finally ended as the Wizards clinched a playoff berth for the first time since 2008.

Wall had scribbled the word “playoffs” on his sneakers to remind himself what this season is all about. Needing just one win to get in, the Wizards came out with a determined effort to make sure that those marker etchings rang true. As the final seconds ticked off at Verizon Center and fans rose to their feet to applaud, Wall took the towel from his shoulder and whirled it around. He then walked up to Coach Randy Wittman, thanked him, and gave him a long hug.

I knew it would be a tough journey, but I didn’t think it would be this tough and this long,” Wall said. “It’s everything I’ve been waiting for as a point guard and trying to learn how to lead in this league and become a better player, but also I think the fans deserve it — the tough time they went through and booing us and feeling bad when we’re not playing good. . . . It took a long time, but I’m kind of happy and excited to say I’m going to be in the postseason, I won’t have an early vacation.”

The rebuilding Celtics offered little resistance against a team that entered the evening clearly on a mission. The Wizards never trailed, shot a season-high 62.5 percent from the field and led by 33 points in the fourth quarter.

Marcin Gortat had his way inside against Boston’s smallish front line and scored 10 of his team-high 22 points in the first six minutes as the Wizards jumped out to a 21-6 lead. Gortat was so loose that he jokingly wound up joining the Celtics’ team huddle during an awkward third-quarter encounter in which Boston point guard Rajon Rondo actually had his arm wrapped around Gortat while addressing his team. After the game, Gortat was even able to convince Wall to dance at center court while the players gathered to celebrate the win.

The Post Sports Live crew debates whether the Wizards would be better off falling to the number 7 seed in the Eastern Conference playoffs and facing the reeling Pacers in the first round. (Post Sports Live/The Washington Post)

“I knew John was a very good point guard and I knew he got incredible dance moves,” Gortat said. “I was trying to convince him for about six months to dance for me. Until that point, I was failing.”

Wall scored just 13 points but he also had a game-high 10 assists to record his 27th double-double, leading some sensational ball movement that resulted in the Wizards handing out 29 assists. Bradley Beal made his first seven field goals and finished with 19 points and Trevor Ariza added 18 points as the Wizards also moved within 11 / 2 games of the Brooklyn Nets for fifth place in the Eastern Conference playoff standings with seven games remaining.

The Wizards (39-36) had lost five of eight entering their game against the Celtics and 15-year veteran Al Harrington could sense that his teammates were still hung over from a deflating loss on Monday in Charlotte. After a gloomy practice on Tuesday, Harrington decided to speak up in the huddle, reminding his teammates they only needed one win to reach the postseason. Harrington (12 points) wanted his teammates to put aside the pressure of playoff seeding and focus on how close they were to accomplishing a goal that they had set in training camp.

“It’s my second year, so I’m fortunate to be a part of a great group and be a part of this at an early age and it’s a good feeling,” Beal said. “To be able to clinch the playoffs ourselves and get the win outright, it means a lot to us. It’s a great group of guys that the front office put together and we just stuck together.”

Washington appeared to be at ease from the start and never let up, shooting the highest field goal percentage in a game for the franchise since April 2001. With the Wizards holding a comfortable lead midway through the fourth quarter, fans began to call for seldom-used Otto Porter Jr., the third overall pick from the 2013 draft, and the rookie from Georgetown paid respect to his supporters as he quickly made a three-pointer from the corner to put the Wizards up 108-81. Porter finished with a career-high nine points in just six minutes.

Since that six-game playoff exit in 2008 — the last of three consecutive first-round losses to LeBron James and the Cleveland Cavaliers — the Wizards bottomed out with a 19-win season in 2008-2009 and rebooted with Flip Saunders before poor chemistry brought about a glitch in those plans.

When Ted Leonsis took over as owner for the late Abe Pollin in 2010, the Wizards started to rebuild around Wall and have had to wait for him to mature while Ernie Grunfeld acquired the right pieces around him. Wittman has also brought more of a defensive mind-set after replacing Saunders two years ago — and now he has led a team into the playoffs for the first time in his career.

The Wizards have been in playoffs-or-bust mode since the preseason, which has led to several all-in moves for the postseason push. They flipped the contract of the injured Emeka Okafor and a first-round pick to get Gortat from Phoenix. They traded failed lottery pick Jan Vesely to get Andre Miller from Denver. And they added veteran Drew Gooden in late February to help the team withstand the absence of their most talented big man, Nene, who has missed the past 19 games with a sprained medial collateral ligament in his left knee.

Wall has blossomed into an all-star for the first time, with Ariza and Beal also putting together career seasons to guarantee that Verizon Center will again host a postseason party — opponent yet to be determined.

“We were in a desperate spot not too long ago,” said Wittman, who joined the Wizards as an assistant five years ago. “When I took over, I just tried to keep telling our guys, Ted and Ernie, let’s do this the right way and build this and teach, and one day, we’re going to get here. We had some ups and downs like you and we’re still learning the process of what it takes to be a really good team. I couldn’t be more happy for these guys.”