LAKE BUENA VISTA, Fla. -- After fouling out of the game in the dying seconds, Kyle Lowry watched the clock tick down on his team's season end, biting hard on the neck of his red jersey in frustration.

A feel-good season that saw the defending NBA champions play beyond virtually every pre-season prediction came to an end when the Raptors didn't live up to their potential, and their own expectations on Friday, done in by uncharacteristic turnovers.

"It's sad that we had more to give, and now we can't give anymore," an emotional Lowry said after the loss.

Jayson Tatum had 29 points while Jaylen Brown added 21 and the Boston Celtics beat Toronto 92-87 on Friday night to take the best-of-seven Eastern Conference semifinal 4-3.

The Celtics move on to face the Miami Heat in the conference final. The Raptors head into an off-season of uncertainty unlike any other.

"They gave everything they had," Raptors coach Nick Nurse said. "Special team."

Fred VanVleet had 20 points, Lowry, who was spectacular all series, finished with 16 points, and Serge Ibaka finished with 14 off the bench for the Raptors.

But the Raptors played like the ball was slathered in butter, committing 18 turnovers. Those giveaways led to 31 points for the Celtics.

"Turnovers killed us," Lowry said. "We were a little bit too fast. We were indecisive in decision-making, that killed us. We were really tentative in some of the things we should have been doing."

Pascal Siakam, who led Toronto in scoring this season before the NBA suspended play on March 11 due to COVID-19, played like a shadow of himself since the restart. He had another off night with 13 points and 11 rebounds in the loss.

"I have to be better," Siakam said. "It was definitely a learning moment for me, just learning from this experience and just learning that you've got to be ready and that I wasn't able to really help my teammates, so, yeah, I take a lot of the blame, man. I take a lot of the blame."

Boston had Toronto's number for most of the season, winning three of four meetings in the regular season to set up what was expected to be a hard-fought series. The seven-game slugfest -- between division rivals who somehow had never before met in the playoffs -- didn't disappoint.

Game 7, appropriately, was a see-saw battle, the lead changing hands 11 times before the Celtics took a 72-71 advantage into the fourth quarter.

The Celtics opened the fourth with a 7-0 run punctuated by a horrible turnover by Siakam.

Did Nurse consider taking Siakam out down the stretch?

"No," the coach said.

A running dunk by Brown had Boston up by eight barely two minutes into the quarter.

The Raptors sliced the difference to just four, but then they unravelled once again due to turnovers, and Boston was back up by 10 points with 4:51 to play.

Toronto rallied once again, Lowry's finger roll and a pair of free throws pulling his team to within two with points. But he fouled out with 35.4 seconds left.

Grant Williams missed two free throws, then VanVleet air-balled a three-point attempt with 12 seconds left, and it was game over for Toronto.

"If you want to achieve something great, if you want to win, it's not going to be easy," Tatum said. "That's what we're here for."

After Kawhi Leonard bolted for the L.A. Clippers last summer, virtually no one expected much from the Raptors this season. But, despite a slew of injuries, they finished second in the East, and continued to turn heads after the NBA restart.

"This team's played fantastically, like wondrously, amazing and we just hit a little bad moment that we did everything we possibly could physically and mentally to work through it," Nurse said. "And we almost pulled it off and we couldn't do it."

Nurse, who won this year's NBA coach of the year, said Toronto didn't play up to its potential against Boston. The fact they were still just a possession or two away from winning the series makes the Raptors' exit that much more painful.

"It's gonna sting," Nurse said. "I think any time that you're bounced out of a season in the playoffs, it does sting for quite a while.

"I was really, really clinging to the notion that if we can find another game to win -- and we did in Game 6 -- and if we can just get one more, maybe we would kind of round into some better play in the next series, and the matchup would switch and it would just get us cooking a little bit more.

"Which goes to (the) question: What might have been?"

Boston won Games 1, 2 and 5. Anunoby's jaw-dropping buzzer-beater to end Game 3 salvaged the series for the Raptors, who went on to take Game 6 in double overtime.

"An unbelievable battle, man," Lowry said of the series. "Those guys, they beat us fair and square. They played extremely hard. They made it tough on us. We made it tough on them. We had opportunities to win it. They came out and did their job and they won and they move on."

Because of the pandemic-delayed season, Toronto was eliminated 456 days after winning the previous title, the longest such run for a team that didn't win consecutive championships.

Now the Raptors, who fly home from the NBA bubble at Walt Disney World on Saturday, head into an off-season of uncertainty. While every post-season break comes with free agency questions, the immediate future of the league is ambiguous right now. While the NBA hopes the 2020-21 regular season can start in December, the coronavirus could wreak havoc with next season as well.

Lowry said he's looking forward to seeing his "babies" -- his two sons, who didn't join him in the Disney World bubble.

Nurse said he has a lot of analyzing ahead of him, including everything from the systems the team runs to player development.

Friday's national anthem was a nostalgic contrast to the fanless arena at Walt Disney World, a reminder of last season's Canada-wide celebration during Toronto's historic Larry O'Brien Trophy run. "O' Canada" was actually footage from Game 5 of last year's NBA Finals, when Toronto opera singer Doug Tranquada led a noisy Scotiabank Arena crowd in a stirring performance.

The Raptors, who had won their previous three Game 7 appearances, came out flat and trailed by 12 points early. But Nurse went to his bench quickly, sparking a 20-4 run capped by a VanVleet three, and Toronto took a 27-26 lead into the second quarter.

The Raptors started to rush their offence in the second, turning the ball over seven times for 13 Boston points. The Celtics had a 15-2 run that turned Toronto's seven-point lead turned into a six-point deficit, and the Raptors went into the halftime break trailing 50-46.

This report by The Canadian Press was first published Sept. 11, 2020.