Trevor Ariza shoots over Boston’s Gerald Wallace during Saturday’s Wizards win.  (Michael Dwyer/Associated Press)

BOSTON – Trevor Ariza was having a rough go early on at TD Garden. He couldn’t make the Boston Celtics pay for giving ample space and time to shoot in the first quarter and was having a harder time keeping up with former Georgetown star Jeff Green on defense.

When Green plowed through him for a difficult layup late in the second period, Ariza went to the bench with three fouls, flustered. But on an afternoon in which Bradley Beal wasn’t the best Bradley in the building, and the Celtics were committed to slowing down John Wall and Nene, Ariza gathered himself in the locker room and carried the Wizards to an impressive 106-99 victory by scoring 19 of his game-high 27 points in the second half.

“Any given night, you never know who has the hot hand. Tonight, it was definitely Trev’s night,” Beal said. “He did a great job stepping up and knocking down shots.”

Ariza’s poor shooting in the first half may have worked to his advantage, since the Celtics didn’t respect him and continued to force Wall to give up the ball. Wall was a willing passer and Ariza repeatedly made Boston pay in the second half for not paying him any mind.

“I was getting a lot of open looks, a lot, a lot of open looks,” said Ariza, whose 14-point third quarter outburst helped his team enter the final period trailing by just two points.

Wall found Ariza for a three-pointer that brought the Wizards within 55-53, but the Celtics extended the lead to 70-62 on a Kris Humphries jumper. Ariza then scored the next nine points for his team, drilling another three-pointer and making a fastbreak layup after Wall stole the ball from Jordan Crawford. He made four free throws to get the Wizards within 74-71 before Martell Webster tied the game on a three-pointer.

Earlier this week, Webster torched the New York Knicks for a season-high 30 points and Ariza said he was content that he could sit back and watch. He added that any of the Wizards’ shooters could do the same if given the chance. On Saturday, it was Ariza’s turn to go off as he made five three-pointers.

“You know it’s going to come back around to you,” Ariza said. “All you’ve got to do is hit a couple of shots and feel good about yourself, then you’re hitting some more shots, you’re getting to the basket. You’re doing everything. Then you’re sitting down on the defensive end, that helps a lot for me, personally, when we get stops and do things like that, it makes the game easy.”

Once his shot started falling, Ariza was more aggressive on the defensive end and helped limit Green to just five second-half points on 1 of 5 shooting. Ariza stole a pass from Green and later fed Kevin Seraphin for a dunk during the game-changing 22-5 run. With the Wizards leading by two late, Wall fed Ariza for a huge three-pointer to put the Wizards up 98-93 and basically knocked out the Celtics.

“Trevor was great. He was in tune the whole night. He had a tough job with Jeff Green, probably one of the best players he had to fight all night,” Coach Randy Wittman said. “He made big shots and we got John, Bradley and Nene that attention is drawn to and we make the next play. That’s the next growth. We don’t force it, when they are going to take me away, I’ve got to give it to you because you’re open and that feeds right down to everybody.”