BOSTON -- The TD Garden crowd roared after what looked like a meaningless rebound in the fourth quarter of the Boston Celtics' 117-103 rout of the Phoenix Suns on Friday night.

But the rebound by Marcus Smart gave the second-year guard the first triple-double of his NBA career.

Smart finished with 10 points, 11 rebounds and 11 assists off the bench, becoming the first Celtics non-starter in 44 years to pull it off.

"Before I got in the huddle, the team was just telling me, 'You know, one more,' and they were telling everyone, 'just box out' and allow me to get the rebounds," Smart said. "That's when I knew I needed one more to get that."

In the first game of a back-to-back, coach Brad Stevens was able to rest his starters in the fourth quarter. Smart took advantage of the 32:31 of playing time and became the first Celtic since the infamous Art "Hambone" Williams (1971) to come off the bench for a triple-double.

"He's getting better every time he takes the court," Stevens said after the Celtics cruised to their second win in three nights. "He did some really good things tonight, including guarding Mirza (Teletovic) when Mirza got going ... and that's what we need him to be. We need him to be a jack of all trades."

Forward Kelly Olynyk, who came in averaging 9.4 points per game, scored 13 straight points in a 22-4 run that ended the first half and sent the Suns (13-28) to their 13th loss in their last 14 games.

Olynyk scored 15 of his 21 points in the second quarter. Guard Isaiah Thomas, traded by Phoenix to Boston last season, had 19 points and five assists in just 24 minutes.

Guard Avery Bradley had 17 points and seven rebounds for the Celtics, forward Amir Johnson scored 13 points and forward Jared Sullinger had 11 points and 10 rebounds.

Bradley said, "I tell Marcus Smart after every game how much I appreciate him."

The Celtics were 14 of 30 from 3-point range against a team that came in 29th in the league in 3-point defense.

The win ensured the Celtics (21-19) will have a winning record at the midpoint of the season for the first time in Stevens’ three-year NBA coaching career.

The Celtics were 14-27 in the first half of Stevens' first year and 15-26 the first half of last season. They hit the official midpoint of this season when they open a three-game road trip on Saturday night at Washington.

Teletovic came off the bench to lead the Suns with 22 points in 21:12. Guard Brandon Knight scored 16 points, forward TJ Warren had 13 off the bench and forward Markieff Morris, making his first start since Dec. 1, had nine points and nine rebounds.

"We let mistakes pile up and snowball, so we have to do a better job once we make one mistake, not making the same mistake over and over again," said Knight, who missed Tuesday night's loss in Indiana with food poisoning.

Phoenix is 1-8 since losing its best player, guard Eric Bledsoe, for the season with a knee injury.

The Suns have lost nine straight on the road.

"You can't give up. I think you have to have a hard head, you have to be positive," Teletovic said.

The Celtics, who scored the last 12 points of Wednesday night's win over the Indiana Pacers, made it 18 straight by taking a 6-0 lead 1:54 into Friday's game. The Suns came back to make it 16-15, but that was as close as they came all night.

NOTES: Phoenix swingman Sonny Weems, who had played 14 minutes this month, logged 23:37 and had 10 points, six rebounds and five assists in the Suns' loss. ... Celtics coach Brad Stevens was pleased to hear Butler, his former employer, established a scholarship in the name of Andrew Smith, the former player who died this week. "It's obviously a great tribute to him, and at the end of the day I think we all knew that they would do something," Stevens said. "I think that will be the first of many types of things established for him. But I know how much he loved Butler and I know his wife appreciates that. So that's a really nice gesture on their part. I'm glad it happened soon. Like, I'm glad it happened really quickly." ... It was last Feb. 19 that the Suns shipped G Isaiah Thomas to Boston after his brief stay in Phoenix. ... Boston F Jared Sullinger went to the microphone to deliver a pregame to salute Martin Luther King Jr.'s birthday. "Without him, none of this is possible," Sullinger said.