TORONTO — It was Tuesday night. The Toronto Raptors — having minutes earlier fallen to the Cleveland Cavaliers in a game that looked close at the end but truly wasn’t — were going about their business in a quiet, solemn, and cramped visitor’s dressing room at Quicken Loans Arena.

Cutting through the silence was a low murmur of subdued conversation. The rattle of a shaker bottle; the clanging lid of a chafing dish. On the whiteboard in the middle of the room, the 10:15 p.m. departure time of the team’s bus to the airport was displayed. Beneath it, someone had scrawled a manifest, all-caps message in green dry erase marker: “RACING CELTICS IN.”

It was a race in many ways. Those Boston Celtics were a couple states over, in Wisconsin, completing their own post-loss rituals after dropping a close contest to the Milwaukee Bucks. Both teams were due for Toronto, where they were scheduled to tip off against one another in less than 24 hours.

Whoever reached their charters first, whoever won the dash to the skies, would be in their beds earlier — theoretically, at least. It was a small race in the context of a much larger one for first place in the Eastern Conference. But maybe that would be the edge.

Whatever the edge was, Wednesday night the Raptors had it. Toronto put up its best defensive effort in weeks, maybe of the season, and got just enough scoring on a cold offensive night for both teams, edging the short-handed Celtics, 96-78. From a playoff-seeding perspective, it was a massively important result.

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Here’s the scenario. With Wednesday’s win, the Raptors lead over Boston atop the Eastern Conference has extended to three games. Each team has four to play, and Toronto holds the tiebreaker. All the Raptors need now to clinch first place — and home court through the Conference Finals — is one more win, or one more Boston loss.

That’s much better than the alternative, in which the Celtics won, moved to within a game of first with the tiebreaker in hand, and played three of its final four against opponents who have lost 50-plus times this season.

“To be a good team, that’s how you’ve got to respond,” said DeMar DeRozan, who led the Raptors with 16 points. “When you have games like we had last night, being able to understand, let’s tighten it up on our mental mistakes and come out the next night and handle business.

“What have we got, four games left? Every single one is extremely important. Next weekend, it’s literally win or go home. It’s no ‘my bad’ or ‘I’ll get the next one.’ These four games, it’s critical on us playing extremely hard and having a rhythm. And understanding our confidence has to be at an all-time high going into [the playoffs].”

The biggest turnaround for the Raptors came defensively. The team was as engaged in its own end as it’s been in some time, and benefitted from a putrid offensive night for the Celtics, who have been playing without several regulars for weeks.

“I liked our defence tonight,” said Raptors head coach Dwane Casey. “I thought our defensive focus was there. Attention to detail. Guys were where they’re supposed to be. A few hiccups, but other than that, I thought it was a big improvement over last night.”

At the other end, Delon Wright had an quietly exceptional game, putting up eight points, eight assists, and nine rebounds, while Fred VanVleet scored 15 off the bench. Serge Ibaka had a terrific fourth quarter, and ended up with 15 on 7-of-13 from the field. And Kyle Lowry bounced back nicely from his rotten performance the night prior, scoring 13 points and finishing a game-high plus-20.

“It’s not redemption — it’s my job to come out here and be professional and be a leader,” Lowry said. “I didn’t make shots tonight again, but I had a better effort. We had a great team effort. We held a great team under 80 points. We didn’t score the way we needed to score, but we played defence the way we needed to.”

In assessing what’s ailed the Raptors over the eight games coming into Wednesday night — in which Toronto lost five, allowed 110 points or more in seven, and generally looked anything but a first-place team — Casey often identified the game’s cerebral elements.

He saw sound passing, rebounding, shooting, pace. But he also saw a team that missed a shot at one end, and lost focus defensively while still obsessing over it. One that allowed an easy bucket, got down on itself, and then failed to execute offensively.

“It’s mental,” he said before Wednesday’s game. “And one thing that cures all that is playing hard. There’s nights you’re not going to be able to make shots. But the one thing that you can do is you can control how hard you play. How hard you compete defensively. How hard you run the floor.”

Wednesday was one of those nights. For all the furor and fuss in the lead-up to this game, the start couldn’t have been much slower. Neither team cracked double digits until the first quarter was halfway through, both looking like they’d played the night prior in a different city as Boston took a 20-14 lead into the break.

Norman Powell got some rare early run thanks to a couple quick fouls on OG Anunoby, DeRozan hit a step-back three over Al Horford, and a motivated Lowry tried to make plays all over the place. But the Raptors shot only 26 per cent (6-of-23) in the quarter. It was not captivating basketball.

The start of the second was similar. The Celtics deployed the ultra-big rotation they had so much success with the last time these teams played, and found similar results, as the Raptors bench struggled to protect the rim.

In response, Casey pulled Jakob Poeltl early in favour of Lucas Nogueira, who immediately made things interesting, as he does. Here’s his very first sequence on the floor, which began with him creating a turnover:

Casey then turned to a three point guard lineup, with C.J. Miles at power forward, and Nogueira at centre. It was an odd one, particularly with the Celtics going so big, but it found immediate success, as the Raptors carried an 11-0 run through the heart of the second.

“You’re looking for five guys who are going to compete,” Casey said. “And those guys came in and changed things.

“It’s called playing hard. Competing. Physicality. I’ll take Kyle Lowry and Fred VanVleet against a lot of 6-6, 6-7 guys just because of how tough they are, and how physical they are.”

That run soon became 20-3, as Wright put in a dominant shift, notching six points, six boards, four assists, and a steal in the quarter. That got the Raptors to halftime with a 10-point lead, having held the Celtics to only 33 points. Toronto also forced Boston into 14 turnovers by half — scoring 22 points off of them — which certainly helped.

The brick fest persisted through the third, as both teams continued to shoot in the mid-30s. The Celtics didn’t score their 50th point until the final minute of the quarter.

“A team like that, they can get hot. We just kind of held our defence down,” Lowry said. “Our defence won the game.”

Toronto’s offence finally heated up in the fourth, shooting 60 per cent in the frame as the Raptors pulled away for good. Poeltl returned and made a pair of nice plays at the rim, VanVleet hit a couple threes, and Nogueira stayed involved with a pair of buckets. Things were mostly said and done by the time VanVleet found Ibaka for this emphatic jam:

“Tonight was big for us,” VanVleet said. “We’re not really concerned about our offence. I feel like we can score with the best of them. Guys are going to get open looks with the way we’re playing this year — really unselfish, moving the ball. But it was good for us to get back to our defensive principles — tighten up a bit, tighten the screws. And kind of impose our will on the game.”

In the end, the Raptors won the small race to Toronto. And they’re now overwhelming favourites to win the big race to the top of the Eastern Conference. Whether or not they’ve fully recovered from their early-spring slump remains to be seen. But if they have, Wednesday night’s win was as good as any to build off of.

“We don’t work this hard and do all this just to give it away,” VanVleet said. “So, in these last four games, we want to close it out.”