PHOENIX — The building went quiet when James Harden went to the free-throw line for three shots after a foul behind the arc by Suns forward Dario Saric in the first quarter.

Down four, the Rockets were off to another slow start. But that soon changed.

Harden made all three, scored 16 of the next 17 points for Houston and secured the lead for good. Rarely does such an energy-killing play create momentum, but these are the Rockets.

On Saturday night at Talking Stick Resort Arena, the Rockets rode efficient scoring from Harden (47 points) and Russell Westbrook (30) in those mano-a-mano moments to defeat depleted Phoenix 139-125 for their third straight victory.

The last time the two teams met, Harden was uncharacteristically quiet, and the Rockets required a fourth-quarter run to pull out a home victory. The Suns have fallen since then, rarely playing with their full team. No Deandre Ayton or Ricky Rubio forced Phoenix into a new starting lineup, with second-year Elie Okobo at point guard, putting pressure on Devin Booker to get his team back on track.

Though Booker has often gone toe to toe with Harden over the years, the games typically end in the Rockets’ favor, with their collective experience and talent too much for the young Suns. That was the case again as the Rockets moved to 20-9.

Perhaps buoyed by their fortunes against Harden back on Dec. 7, the Suns opted to play far less aggressive defense than Harden has seen most of the year. The former Arizona State star required 27 shot attempts to get his 34 points when the Rockets hosted the Suns that night. Without Rubio — who often checked Harden during playoff series between the Rockets and Utah the past two years — the Suns on Saturday mostly defended Harden with just one defender.

The primary defensive stopper for the Suns against the Rockets’ stars, Mikal Bridges, got into early foul trouble. That left Booker, Kelly Oubre Jr. and rookie Ty Jerome to defend Harden. He happily took advantage of the lack of attention to record one of his more efficient games of the year.

By the end, Harden was clearly gunning for 50, looking to friends sitting courtside after each made 3-pointer. Though he didn’t get it, the 47 points were Harden’s highest total since Dec. 13.

Not only did Harden punish the one-on-one defense by scoring, he also found Clint Capela repeatedly for lobs that the Suns, without Ayton, could not contest. Capela was nearly perfect from the field, scoring 14 on 7-of-8 shooting.

Typically dependable to create a bucket in such situations, Booker, clearly bothered by the right forearm injury near his shooting hand that cost him three games this month, was quiet. The Rockets’ stars dominated while the Suns’ were either inactive or ineffective.

A failed coach’s challenge by the Rockets’ Mike D’Antoni midway through the second period — on a Harden charge — paused the action and spurred a mini run by the Suns. Booker continued to look to pass, and Phoenix pierced mismatches allowed by the Rockets’ switching defense, tallying 19 assists on 24 made baskets as a team in the first half. It was the only promising spurt all night for Booker and the Suns (11-18).

By the time Booker dialed up his aggressiveness, the game was out of reach. The Rockets turned a five-point halftime lead into an 11-point lead going into the final period. D’Antoni sent both of his stars onto the court to start the fourth and finish the job. Their offensive power was too much for Booker to match singlehandedly.

Booker scored just 19 points in 34 minutes.

For the second straight game, Harden and Westbrook (10 assists) each scored 28 or more points. The star guards have also been doing it efficiently. Against Phoenix, both shot better than 50 percent from the field and set up teammates with ease.

Based on the way the Suns played Harden, perhaps teams are starting to adjust to Westbrook’s place on the Rockets in a way they did not before. When Harden was out of the game, Westbrook operated comfortably with the ball in his hands, isolating, drawing fouls and running the break like the Westbrook of old.

He finished plus-12 compared with Harden’s plus-2, a symbol of how the Rockets’ were able to increase the lead when Harden was on the bench — and potentially a signal of a promising shift for the Rockets moving forward.