DENVER — The third quarter was when it all unraveled, when the Phoenix Suns lost their grasp on Game 5 and perhaps their grasp of this Western Conference semifinals series altogether.

Phoenix quelled an opening 9-0 punch from Denver in the contest’s first frame Tuesday night, when the combination of Devin Booker’s efficient sniping and Kevin Durant overcoming a 1-of-9 shooting start clawed the Suns to within 3 points at intermission. Only one team emerged ready for the second half, though, as the Nuggets began that fateful third period on a 17-4 run from which Phoenix never recovered. Denver built an advantage as large as 21 and dug a hole so deep, by the fourth quarter, the Suns sent a five-man lineup of reserves to the scorer’s table with almost five minutes still remaining in the game. The Nuggets would finish with a 118-102 win, claiming a crucial 3-2 series advantage.

“When we got down, you could see the faces weren’t as strong as they typically are,” Phoenix head coach Monty Williams said.

Veteran point guard Chris Paul, sidelined with a strained groin for the third consecutive game, tried to coax a change of spirit in several huddles, but Williams saw a lack of composure that his roster maintained and exerted during their two straight victories at home in the desert.

“You have to have a level of mental stamina in the playoffs,” Williams said. “You have to keep your level of poise at a productive level, so no matter what happens on the floor, you can always run your stuff or rely on your defense.”

After his own sluggish beginning, shooting just 1-of-6 from the field in the first half, Jamal Murray set the Nuggets’ second-half tone that withered the Suns’ resolve. He rammed his backside into a stringier defender, Landry Shamet, and found his way to a pair of layups — the second a bruising finish past Shamet with Murray spouting a string of junk in his opponent’s direction that prompted a technical foul from a nearby official.

“I’m just trying to get myself going sometimes,” Murray said. “Sometimes, you know, I just need a little energy boost for myself. Once I’m in attack mode, then it kinda changes the game.”

Attack Denver did. Two minutes after Durant was whistled for a moving screen trying to free Booker lose, Murray met the Suns’ interminable scorer at the rim with 6:48 left in the third, drawing a fourth foul on Durant that caused Williams to sit the 13-time All-Star for whom Phoenix emptied its war chest to acquire at February’s trade deadline.

That’s when Denver’s lead first ballooned to 20, with a 77-57 edge. The Nuggets finally nullified Booker’s offensive eruption throughout these entire playoffs during that stretch. He had opened the game a sizzling 5-of-8 from the field en route to 19 first-half points, but Booker shot just 1-of-8 in the third quarter. He saw wave after wave of defenders and appeared to drown without a life raft or some form, any form, of supplementary offense with Durant on the bench. Nikola Jokić swatted his layup attempt. Booker airballed one 3-point look from the left wing. He missed a pull-up in the lane.

“I thought a lot of what they did was to make everything tough on us,” Williams said. “They ran two or three guys at Kevin and Book tonight. They tried to bottle them up.”

“We were the aggressors,” said Jokić, Denver’s two-time MVP center who passed Wilt Chamberlain with his 10th postseason triple-double, tying the fifth-highest total in NBA history. Jokić finished with 29 points, 13 rebounds and 12 assists in the rout. “The two games in Phoenix, they were the ones who were pushing us all over the place, off our spots, digging into us.”

The Nuggets succeeded in grounding Phoenix’s whirring offense from Games 3 and 4. After Nuggets head coach Michael Malone spoke pregame about limiting the Suns’ opportunities in transition, Denver outscored its competition 31-25 in the open floor. Malone long ago learned from his father, Brendan Malone, who spent over 40 seasons on sidelines across the NCAA and NBA map, the value of learning from players during film sessions. And feedback from his roster following consecutive losses indicated the Nuggets’ players wanted to pressure Booker from the moment he touched the ball, on any inbounds pass 90-plus feet from the basket.

“We [were] letting Devin Booker just walk the ball up every time, lead double drag, get to his spot and beat us,” Malone said. “So let’s be an irritant.”

The Nuggets capitalized on that game plan in spades. They received the complementary contributions the Suns so desperately lacked — Bruce Brown providing 25 points off the bench, Michael Porter Jr. draining four triples in the opening period, rookie wing Christian Braun ripping a steal and flushing a two-handed jam over Durant. Next to Murray’s locker, taped onto a black wall, there’s a printout of Bruce Lee and the quote, “Knowing is not enough, we must apply. Willing is not enough, we must do.” The Nuggets understood their task and, frankly, did it all evening long.

Denver is 6-0 at home in these playoffs. The Nuggets may not return to this hardwood floor 5,280 feet above sea level until the Western Conference finals if the Nuggets can take care of business in Game 6 at Phoenix on Thursday.

Paul’s status for that possible elimination game remains in question. He was on the court, shooting with assistant coach and close friend Jarret Jack during pregame activity, and did not look especially comfortable attempting to convert five straight makes at different spots along the 3-point arc. The Suns are quite familiar with the difficulty of returning from that affliction. Booker came back too soon from his own groin injury on Christmas. And after playing just four minutes, he reaggravated the issue, leaving him inactive for Phoenix’s next 21 games.

Even with Phoenix’s season in the balance, Paul is still 38 years old, and the risk of losing him for a deeper stretch of the postseason — which Suns personnel surely still believe is attainable — will certainly factor into whatever calculus leads his rehab over the next 48 hours.

“We've got to win when we go home,” Williams said, “so we can come back and play here."