Two weeks after losing by 54 points in Boston, the Toronto Raptors handed the Celtics their most humbling loss of the season Wednesday night.

Toronto led for nearly the entire second half and held Boston to 15 fourth-quarter points in a 110-97 victory at Scotiabank Arena.

Despite facing two of the NBA’s worst teams in consecutive games, the Celtics are a missed CJ McCollum layup away from a three-game losing streak, bookending double-digit defeats against Sacramento and Toronto around a one-point home win over New Orleans.

“Obviously, we’re not playing our best basketball,” Celtics coach Joe Mazzulla told reporters postgame. “You can’t expect anything to be easy, and you can’t have an expectation that it’s always supposed to go your way, because it’s not. We just have to find a way to enjoy the challenge but make sure we do it together.”

Kristaps Porzingis (18 points, 7-for-11 shooting, 4-for-5 from 3-point range) and Payton Pritchard (20 points, 7-for-11, 4-for-8) were bright spots for Boston on Wednesday, but the Celtics were outclassed by a 10-31 Raptors team that will be in the running for the No. 1 overall draft pick.

Porzingis’ review of the Celtics’ performance was much harsher than Mazzulla’s.

“I think we played with no spirit, with no personality,” the big man told reporters in Toronto. “It was just a weak performance from us, honestly. We just played with no personality.”

He added: “It feels like (expletive) right now, and we played some bad basketball.”

It was an especially rough night for Jaylen Brown, who went 3-for-15 on two-point shots and was a minus-23, and for Derrick White, who played arguably his worst game of the season. White went 2-for-9 and 1-for-7 from three, scored six points and finished with one assist and no rebounds, blocks or steals in 21 minutes. The Celtics were outscored by 29 points with the typically reliable guard on the floor, White’s worst mark of the season.

Brown and Jayson Tatum combined for a season-low 26 points in the loss, with Tatum leading the Celtics with 10 rebounds and seven assists.

RJ Barrett, who missed Boston’s 125-71 decimation of his squad on New Year’s Eve with an injury, led a balanced Raptors effort with 22 points, 11 rebounds and eight assists.

Next up for the Celtics is a back-to-back at TD Garden this weekend. They’ll host the Orlando Magic on Friday and the Atlanta Hawks on Saturday — two teams that already have beaten Boston this season.

The Raptors opened up a 10-point lead less than four minutes in, starting 5-for-6 from the field against a Celtics defense that lacked the necessary juice. Boston dialed in after an early Mazzulla timeout and quickly erased that deficit.

Porzingis keyed the Celtics’ rally with a steal in the lane, a block at the rim, a driving dunk off a Jaylen Brown feed and a pair of 3-pointers. Pritchard also gave Boston a needed spark off the bench. From the time the Sixth Man of the Year favorite entered at the 8:33 mark through the end of the first quarter, the Celtics outscored the Raptors by 14 points. A Pritchard three gave them their first lead of the night, 27-25.

Boston built a seven-point cushion early in the second quarter, then saw their poise waver again. Toronto ripped off a 17-3 run to surge ahead, during which the Celtics had more offensive turnovers (two) than defensive stops (zero).

The Celtics rallied again late in the first half – Tatum and Al Horford each hit a three; Pritchard hit two, including one from the corner with one second remaining – but still trailed 55-53 at halftime. It was Boston’s first halftime deficit since Dec. 27.

Pritchard and Porzingis – whose outside shooting has greatly improved since he returned from the ankle injury he suffered on Christmas – each scored 13 first-half points. Tatum and Brown totaled just 11 on 4-for-17 shooting.

The Raptors then proceeded to hit 10 of their first 11 shots in the third quarter, with all five of their starters reaching double figures by the end of the frame. Jakob Poeltl, who torched the Celtics when these teams met at TD Garden back in November, made all five of his third-quarter field goals as part of an 8-for-8 night (16 points, 11 rebounds).

Late in the third, with Boston down seven, Raptors wing Scottie Barnes stepped toward Tatum while guarding him near halfcourt and clapped in the Celtics star’s face. Tatum responded by blowing past Barnes as he rocketed toward the basket – but rang front iron on what would have been an arena-shaking dunk.

That missed slam exemplified an ugly third quarter for the Celtics, who consistently were a step behind the hot-shooting Raptors. And things got even worse for Boston in the fourth.

Toronto took an 88-82 lead into the final quarter. Less than two minutes later, it was 94-84. The Celtics never got back to within single digits, and Mazzulla waved the white flag late, emptying his bench with 1:22 remaining.

In the fourth quarter, the Celtics shot 6-for-21, allowed seven offensive rebounds and made two of their eight free throws (they were just 9-for-18 from the line in the game). White sat most of the fourth in favor of Pritchard as he works through a brutal shooting slump. Since missing Boston’s Jan. 7 win at Denver with an illness, White has shot 4-for-23 from the floor over three games (17.4%). He’s 3-for-29 from three over his last four outings (10.3%).

And it’s not just White who’s scuffling. The Celtics’ entire starting lineup has been lacking in its limited minutes together this season.

The grouping of White, Tatum, Brown, Porzingis and Jrue Holiday had been outscored by 8.9 points over 100 possessions entering Wednesday – one of the worst net ratings in the NBA – and those five players have not recorded plus/minuses above zero in any of Boston’s last three games. Tatum’s minus-1 was the best of the bunch against Toronto.

Wednesday’s loss dropped Boston to 28-11 on the season, 7-7 in its last 14 games and 5-5 when its preferred starting five is available – all marks that are well short of the Celtics’ championship-chasing standard.

“We’ve just got to continue to stick together,” Mazzulla told reporters. “Work on the details, the effort, the execution, just the little things that go into it. … It’s more about just having an understanding of where we’re at and where we’re trying to get to and work through it.”