Marcus Smart said a courtside heckler was chirping at him during the Celtics’ 109-106 win over the Grizzlies on Monday in Memphis, Tenn. It spurred Smart to his one of his best games of the season. Brandon Dill/Associated Press

Marcus Smart had his best game of the season in Boston’s 109-106 win over the Memphis Grizzlies on Monday night. It turns out he had a little help from a courtside heckler.

The Celtics point guard had 15 points and a season-high 12 assists, in part, because of the chirping he was receiving from a fan sitting courtside in Memphis. Smart and the fan were going back and forth throughout the game – and much like Reggie Miller used Spike Lee’s heckling to his advantage decades ago – it helped inspire the Celtics guard’s performance.

“I had a heckler on their sideline kind of going crazy,” Smart told NBC Sports Boston after the game. “It kind of gave me a little bit more motivation to come out here and just play the best basketball I can.”

Smart was locked in from the opening tip as he scored or assisted on the Celtics’ first 16 points of the game. He was making the right plays all game as he continued to shake off a less-than-ideal start to the season. Coupled with 11 assists in Saturday’s win over the Knicks, Smart has 23 assists to just three turnovers over his last games.

His performance also included a highlight-reel three-point play as the Celtics pulled away in the fourth quarter. The Celtics led by five midway through the quarter when Smart drove to the lane, took contact from Santi Aldama and acrobatically floated the ball in with his left hand as he crashed to the floor. Smart looked at his hand in awe and pointed at it to celebrate the play.

JA MORANT IS one of the toughest covers in the NBA but the Celtics made life tough for him when it mattered most.

Boston’s stout defense limited Morant to just three fourth quarter points on 1-of-6 shooting from the field.

Jayson Tatum had a couple blocks against Morant in crunch time but it was a full-team effort defensively against the speedy point guard as Grant Williams, Al Horford and Smart all took turns against him in the fourth quarter.

When Coach Joe Mazzulla was asked after the game whether Tatum asked him to guard Morant late, that team mentality appeared once more.

“Our whole team asked to,” Mazzulla replied.

The Celtics went with a bigger lineup look to start the game against the Grizzlies with Grant Williams starting over Derrick White. Boston closed with the same lineup and that grouping helped limit Memphis to just 21 fourth quarter points on 42.9 percent shooting.

“Our guys have always played hard but tonight I felt like we took a step towards our defensive details,” Mazzulla said. “Our positioning, our attention to detail as far as personnel. Everything we talked about, our guys did a great job carrying that over.”

Mazzulla also gave no hint on whether the switch in the starting five would be a permanent one or a one-time shift.

“Just thought that gave us the best chance to match up,” Mazzulla said of the move.

Boston still ranks just 22nd in defensive efficiency after Monday’s win but the team certainly took a step forward defensively after struggling to consistently slow down the Knicks and Bulls offense throughout their last two wins. The Celtics will have a chance to sustain that momentum on Wednesday night against a Pistons squad that has one of the five-worst offenses in the NBA to begin the year.