TORONTO — Dwane Casey asked his team to play with pride.

Facing an ugly ending to a season that had held so much promise, the coach didn't want them to go down without a fight.

They responded. But in the minutes after the Toronto Raptors' season came to an end in a four-game sweep by Cleveland in the Eastern Conference semifinals, Casey lamented the three lackadaisical efforts earlier in the series.

"It's tough," Casey said. "We know we could have played better in the first three games. We didn't.

"Today, I thought the guys played. In that do-or-die situation, guys can easily pack it in. I thought our guys played with grit, toughness, togetherness. I think it's a testament to their character and the culture that those guys have created. We all want to win. I don't know if we're there yet. We're knocking on the door."

Serge Ibaka scored 23 points, while DeMar DeRozan added 22, and the Raptors, coming off three consecutive blowouts, took Cleveland to the final couple of minutes before dropping a 109-102 decision to the defending NBA champion on Sunday.

"At the end of the day, you gotta give (Cleveland) credit," said a downcast DeRozan, his young daughter Diar — dressed in a white sequined No. 10 Raptors jacket, propped on his lap. "They're a hell of a team for a reason. They got one of the greatest players of all time (LeBron James).

"It's on us to let this sink in and understand we gotta come back extremely better, individual and team-wise. It's something that we got great experience with playing these guys two years in a row. We just gotta figure it out. We gotta figure it out."

It was Toronto's first playoff sweep since the opening round against Washington in 2015. Now the Raptors head into an off-season of uncertainties, including questions around the future of Casey and Kyle Lowry, who plans to opt out of the last year of his contract and become a free agent.

"It's hard to break down a team that won 50-plus games two years in a row, with the core guys," DeRozan said. "That's on upper management. Us as players, we've gotta be ready for whatever. The guys that are free, the guys that are coming back, we've gotta understand, we've gotta work on our game, become better, and leave it up to the front office to figure out everything else."

LeBron James had 35 points to top the Cavs, who dispatched the Raptors in six games in last season's Eastern Conference final. Kyrie Irving had 27 points, while Kyle Korver finished with 18.

Cory Joseph, who started for the second straight game in place of an injured Lowry (ankle) had 20 points and 12 assists, while P.J. Tucker, who was draped all over James on the defensive end, finished with 14 points and 12 rebounds.

James applauded Tucker's defensive efforts, saying "Any time you go against someone who wants to compete, you respect that and P.J. has been like that since we were kids. . . he's always been a guy that at the end of day is never going wonder if he left it all on out there and as a competitor I can always respect that."

Hoping to stave off elimination, the Raptors were aggressive from the opening whistle. They were making shots. The Cavs were missing. And Toronto went up by 11 points — their highest lead of the series.

But the sharp-shooting Cavs weren't cold for long. Their three-point shots, whether uncontested or contested, started falling, and can't-miss Korver, who was acquired in January from Atlanta for nights just like this, had four in the second quarter alone. The Raptors' lead had morphed into a 16-point deficit by early in the third quarter.

The Raptors, though, found another gear in the third, and when Tucker launched a three with 0.8 seconds left in the quarter, it cut Cleveland's lead to 85-80 with one quarter left.

Fuelled by a raucous white-clad Air Canada Centre crowd that included Drake, NBA commissioner Adam Silver, and Toronto FC's Jozy Altidore and Eriq Zavaleta, Ibaka scored and drew a foul in front of the Cavs bench. His free throw gave the Raptors a one-point lead with 6:38 to play.

But Irving responded with 11 straight points to put the Cavs up by eight, then James drained a three over Tucker with 2:54 to play that capped a 14-2 Cavs run. The Raptors responded, and a three in front of Cleveland's bench cut the deficit to five points with 25 seconds left, but a pair of Korver free throws sealed the Raptors' fate.

The ACC crowd applauded the Raptors as they walked off the floor.

The Cavs face either Boston or Washington in the conference finals.

"They're a great team," Tucker said. "It's going to be hard for somebody to beat them four games."

Casey also lamented the few games the Raptors' core had after acquiring Ibaka and Tucker in February. Lowry missed 21 games at the end of the regular season, and had just a handful of games with the newcomers.

"It's hard to say," said Casey, before trotting out one of his favourite sayings: "Ifs and buts are candy and nuts and we'd all have a Merry Christmas.

"But nobody really cares," he added. "I know Cleveland didn't care. You always would love to have a training camp with the group to start from scratch but we didn't. I was so happy and it was a great move by our organization to get (Tucker and Ibaka) because they stand for what we needed. We just picked a bad number to draw in the second round. I think we picked a team to go against that was a buzzsaw."

DeRozan wasn't having any talk of what ifs.

"If we had LeBron on our team too, we would've won," DeRozan said. "We can say that all day, time, everything, we didn't. It happened. We got swept. It's gonna be one of them long summers for us."

The Raptors shot 47 per cent on the night, and, after connecting on just two three-pointers in Game 3, went 10-of-29 from long range. The Cavs were 16-of-41 from the three-point line. The Raptors also coughed up 17 points on 13 turnovers.

DeRozan, who was coming off a career playoff high 37 points, went down in a heap in the second quarter after taking a knee to the groin from Iman Shumpert. Lowry, in a black suit jacket, walked gingerly across the court to help up his injured teammate. Shumpert received a technical, and the ACC crowd groaned in unison when the replay was shown on the Jumbotron.

Ibaka's three-pointer with 4:05 left in the first quarter — Toronto's third three of the game — had the Raptors up by 11, but James responded with a three to spark a 13-2 Cavs run, and the first quarter ended all tied up at 28-28.

Korver came on in the second, and instantly spelled trouble for Toronto. His fourth three of the quarter gave the Cavs a 14-point lead just under a minute before halftime, and Cleveland had a 61-49 advantage at the break.

A three by James gave the Cavs a 16-point lead at 10:05 of the third, but threes by Joseph, Ibaka, and Powell sparked a Raptors rally that saw them twice pull within five points late in the third.

The Cavs won the first three games 116-105, 125-103, and 115-94.