TORONTO — They'd built a huge lead, the three-point shots were falling — finally — and the Toronto Raptors looked headed for an easy rout of the lowly Chicago Bulls.

The Bulls, however, thought otherwise.

Jonas Valanciunas had 21 points — including just the second three-point shot of his NBA career — and 10 rebounds, but the Raptors were forced to fend off the Bulls' feisty fourth-quarter comeback in a 119-114 victory on Tuesday.

"The hardest thing to do in this league is hold a lead," said Raptors coach Dwane Casey. "You get a big lead and you think the game’s over, you turn it off mentally and that's exactly what we did tonight."

DeMar DeRozan had 24 points for Toronto (6-4), while Kyle Lowry finished with 17 points and Serge Ibaka chipped in with 16.

Bobby Portis had 21 points to top the Bulls (2-7), while Robin Lopez had 20.

"It wasn't how we wanted to close it out, but a win is a win," Lowry said.

Valanciunas, who scored the first three-pointer of his five-season NBA career just last April, drilled the step-back three late in the first quarter, then calmly raised three fingers like he does it every day.

The big Lithuanian was one of eight Raptors who scored on three-pointers on a solid shooting night. The Raptors shot 54 per cent, and 52 per cent from three-point range.

"It's always good, especially when we move the ball like we move it, guys getting open shots that guys work on every day," DeRozan said. "Get the ball moving around, and seeing it dropping builds confidence."

The three was one of the few highlights on an otherwise largely forgettable game. The Raptors had assembled a 20-point lead before halftime against the rebuilding Bulls, stretched it to 23 in the third quarter and led 98-81 with one quarter to play.

But 14 fourth-quarter points from Portis — who was playing his first of the season after serving an eight-game suspension — propelled the Bulls back into the game.

"Bobby gave us a great lift out there," said Bulls coach Fred Hoiberg. "He played with great emotion and went out there and gave us energy when we needed it."

A goaltending call on a Denzel Valentine shot with 19 seconds to play made it a three-point game, but DeRozan drained two free throws to secure the win, much to the relief of the Air Canada Centre crowd of 19,800 that included Nick Hagglund and Jonathan Osorio. The Toronto FC players fired T-shirts up into the crowd during a timeout.

"I think we kind of just got comfortable playing with a lead," said Norman Powell. "That's one of the toughest things to do in the league is continue to have your foot down when you're beating a team like that. Just continue going thinking it's 0-0, that it's a close game, just trying to close it out. We've got to do a better job of coming out with the same sense of urgency we had in the first half."

C.J. Miles had obviously shaken the flu bug that knocked him out of Friday's game against Utah and slowed him down on Sunday, scoring back-to-back threes to give the Raptors a six-point lead late in the first quarter. Toronto went into the second up 29-26.

A Portis layup pulled the Bulls to within two early in the second, but the Raptors outscored Chicago 21-13 from that point to take a 65-45 lead into the halftime break — the second-most halftime points Toronto has put on an opponent this season.

The Bulls are still missing Nikola Mirotic, who suffered broken bones in his face in an ugly brawl in practice with Portis prior to the season-opener, resulting in Portis's suspension.

The Raptors host New Orleans on Thursday, then head on the road for three games starting Sunday in Boston.