BOSTON -- They had the best record in the NBA and had just come off a 16-game winning streak. But that doesn't mean the Boston Celtics were doing everything right.

In short, their offense wasn't matching their defense, especially at the start of games, and their bench was coming up short.

But Friday night, with the floundering Orlando Magic barely getting in the way, Boston erupted for 40 points in the first quarter and 73 in the first half -- both season highs -- on its way to a 118-103 rout that sent the Magic to their seventh straight loss.

The 118 points also marked a season high for Boston, and the Celtics matched their season best with 17 3-pointers.

"Offensively, as a team we've been struggling," Terry Rozier said after his career-high 23 points helped raise the record to 17-3 -- matching the second-best 20-game start in franchise history.

And much of the problem, aside from slow starts, had been a lack of production from the bench. Rozier's 23 was part of a 50-point bench effort.

"It just feels good," said Rozier, who smashed his previous high of 16. "It feels good to get points as a unit."

The win was also the 14th straight for the Celtics, winners of 17 of their last 18, over the Magic, who haven't won at TD Garden since 2010.

Kyrie Irving scored 30 points and Al Horford matched a career high with 10 assists (seven in the first quarter) in the second win in as many tries against Orlando (8-11) this season.

The emphasis was on swinging the ball to the opposite of the floor for open shots. The plan was followed, with Celtics coach Brad Stevens saying, "We didn't meet at all the last two days, but that message was sent out, and hopefully we continue to play that way."

Irving did his damage in 24:52, becoming the first Celtics since Kenny Anderson in 2000 to score at least 30 points in 25 minutes or less.

Rozier had just six field goals in the last five games and went 8 of 11 from the floor and 5 of 7 from 3-point range. He also had six rebounds in 30 minutes off the bench.

"Any way you put it, I'm going to keep shooting," he said. "I'm going to keep playing. Iā€™m not perfect. I'm going to have tough games. I'll have games like this. It just feels good."

With the Celtics playing Saturday night at Indiana, Stevens got to clear his bench early. Marcus Morris was the only starter to play in the fourth quarter, when Orlando showed its only sign of life.

Morris, who has a sore knee, didn't travel with the team postgame and will miss Saturday night's game to rest. Jaylen Brown said he could miss the game if he doesn't make it there in time after his friend's funeral in Atlanta.

Down by 30 at the end of three quarters, the Magic managed to get as close as 14 with just under four minutes left. They have played at TD Garden three times in this calendar year and have allowed at least 92 points in the first three quarters of all three games.

"We are not good enough defensively right now, but Boston was clicking on all cylinders," Magic coach Frank Vogel said. "They are a great team, their record is what it is for a reason and give credit to them."

Aron Baynes had 12 points and a season-high 10 rebounds, Brown scored 13 points and Jayson Tatum had 11 in the victory.

Horford is the only player in the NBA to be a plus in every game this season. He entered the game fourth in the league in that category and is now a plus-185.

Jonathan Simmons came off the bench to lead five Magic players in double figures with 14 points. Nikola Vucevic had 12 points and 11 rebounds.

"They are a really good team," said Aaron Gordon, who had 11 points but went just 2 of 10 from the floor for the Magic. "They execute offensively very well. Defensively, they don't have a lot of breakdowns. We had too many breakdowns and they take advantage of that every single time."

NOTES: The Celtics debuted a new black jersey on Black Friday. ... Orlando coach Frank Vogel, talking before the game, called Boston C Al Horford "Probably the most underrated guy in the league, in my opinion, for everything he does." ... Talking at the morning shootaround, Magic C Nikola Vucevic said, "We need to play at our best tonight. We can't have any stretches where we don't compete on both ends. They're a great team. They've been playing great." ... The Magic continue their four-game road trip Saturday night at Philadelphia. ... On Monday night, Boston hosts the Detroit Pistons in the first return of former Celtics Avery Bradley, traded to Detroit for Marcus Morris during the offseason.