The Celtics entered Sunday night’s contest with the Washington Wizards as -20.5-point betting favorites. It was their largest spread since being 22.5-point favorites against the Miami Heat in 2008.

There’s a reason that line was so high.

One of these teams is riding high into the postseason, winners of 13 of their last 15, looking to defend their title in June. The other had lost 11 of their last 15 and are free-falling to what will likely be their second consecutive season failing to reach 20 wins.

And it played out exactly as expected.

Photo credit Bob DeChiara-Imagn Images

The Celtics ran the lowly Wizards out of the gym with a 124-90 win. Boston led by as many as 36 and never trailed. The only tie came at 0-0. Jaylen Brown, Derrick White, Al Horford, and Jrue Holiday got the fourth quarter off in a game so one-sided that Brown was tossing t-shirts into the crowd during the fourth-quarter t-shirt contest.

“I was a little disappointed. He didn’t have a smart way of doing it,” White said on Brown’s t-shirt toss. “The spin was knocking it down. He needed to throw a spiral. I’ve got to help him out.”

Brown’s toss may have been the only thing worth critiquing. Against a Washington team embracing the tank, sitting a healthy Marcus Smart, the Celtics came out and did their jobs, blowing out a team they were supposed to, with contributions from up and down the roster. But it wasn’t talent alone that got the Celtics this victory. In a game with little meaning to the Celtics, they came out and dominated, playing with effort and intention for an entire 48 minutes – which was reflected in the margins of the box score.

The Celtics outshot the Wizards by 12, had 30 (!) more rebounds, and had nearly as many assists (33) as Washington had made field goals (35). It marked the first time since 1972 that the Celtics were a +30 in scoring and rebounding. It was just the second time since 1995 that the Celtics had at least 60 rebounds and 30 assists.

Twenty-five of their season-high 62 rebounds came on the offensive glass, where Boston held a +14 edge (25-11) — matching their highest single-game total for offensive boards since the 1999-2000 season.

“For the most part, rebounding is a testament to the effort level and the attention to detail level. The things that we have to get better at,” head coach Joe Mazzulla said. “That’s an area that you can get extra possessions on, and we have to fight for that. The guys really locked in on that, and it was good for us.”

Seven different Celtics grabbed an offensive rebound, with six pulling down at least two. Luke Kornet led the way with nine, a new career-high. Over the last 25 years, only five other Celtics have reached that mark: Brandon Bass, Robert Williams, Aron Baynes, Kendrick Perkins, and Jared Sullinger.

“He’s unbelievable,” Derrick White said of Kornet’s on the offensive glass. “He just seems to always be in the right place. He just kind of makes the game easy for everybody, and if there is a miss, you always know Big Luke’s down there, most likely, to get a hand on it. He’s been unbelievable for us all year.”

Photo credit Bob DeChiara-Imagn Images

Jrue Holiday added five offensive boards — his most in a Celtics uniform and the most by a Celtics guard since Rajon Rondo in 2010. All told, Boston’s 25 offensive rebounds turned into 32 second-chance points.

“The difference in the game was the offensive rebounding, especially in the second half. I thought we were making a little bit of a push to get back into it, but they had 26 second-chance points, and a lot of those ended up being three-pointers,” said Wizards’ head coach Brian Keefe. “To me, that was the biggest difference in the game. They had too many second-chance points.”

Of course, many will also point to the three-point shooting — and rightfully so. Boston went 24-of-52 (46.2%) from deep, improving to 22-3 when making at least 20 threes. But it’s how they got those looks — with dominance on the glass and 33 assists — that tells the real story of Celtics basketball: find every advantage you can and capitalize on it.

“There are so many different ways for us to attack teams. Just trying to create an advantage and try to keep that advantage,” said White. “I think we did a really good job of hitting offensive glass, which kind of created more open looks. That’s really where all my threes came from, the second chances. So just hitting off in the glass, just doing the little things to impact winning.”

Those little things loom even larger in the playoffs. That’s why the coaching staff has been hammering the importance of rebounding — one of the simplest ways to steal extra possessions. The Celtics are now 38-7 when they match or outrebound their opponent. Last season, they went 44-7. They didn’t lose a single game in the playoffs when they won the rebounding battle.

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“Earlier in the year, we kind of struggled on the rebounding aspect, but I think after All-Star break, we’ve been really good. That’s been a point of emphasis for the coaching staff and us,” said Sam Hauser. “If we’re going to go far in the playoffs again, we have to rebound and win that margin of the game.”

Mazzulla insists the recipe for winning doesn’t change come the postseason. If anything, it’s just heightened.

His coaching philosophy is rooted in controlling what’s within reach — the margins, the intangibles: effort, intensity, and focus — and exploiting the nuances of the game. It’s something the players understand and execute, knowing its importance, especially as playoffs near.

“You always want to find extra possessions,” said White. “Just trying to find those little ways to help us get an advantage. I think we’re just doing a good job of just trying to find different ways to win.”

It’s no surprise that as those details have sharpened, the wins have piled up. Boston has won 19 of 23 since the All-Star break, leaving the head coach pleased with the direction his team is heading as they gear up for the big dance.

“Just playing winning basketball. Twenty-five offensive rebounds, that’s a commitment,” Mazzulla said. “Communication, the little things. You are going to give up stuff in every game, but there is an awareness of the competitiveness that we have to have. The execution that we have to have. The open-mindedness to do different things. You don’t know who you are going to play [in the playoffs]. You don’t know what the matchups are going to be. You don’t know what they are going to try and exploit. Every team is better than us at something. So we have to be as versatile as we can to go to what we need to go to, depending on who we’re playing and the guys who are buying into that. They are competing. We need to keep that up.”

Just like last season, controlling the margins and what they can control will be the focus as the Celtics head into the playoffs — and it’s a habit that’s easier to carry over now, given how much they’ve ramped it up in recent weeks.