Stoudemire had 19 points and 10 rebounds, and the reserves keyed a big second quarter for the Suns in a 101-85 victory on Monday night.
"They gave us a lead, a comfortable lead, and we came out in the second half and kept it going," said Stoudemire, who fell one point shy of his fifth straight 20-point game.
Goran Dragic scored 10 first-half points off the bench and the reserves had 24 of 33 second-quarter points, when the Suns quickly erased an early double-digit deficit.
Channing Frye scored seven points in the second quarter and Louis Amundson added five points, five rebounds and a pair of blocked shots in the period as the Suns outscored Denver 33-11 to turn a 13-point deficit into a 57-44 halftime lead.
"It happened so fast," said Carmelo Anthony, who finished with 17 points on 7-of-21 shooting.
The Nuggets, baffled by the Suns' switch to a zone defense, were held scoreless for 5:23 after taking a 37-24 lead and shot 5 of 16 from the floor with nine turnovers. Denver's 11 points in the quarter were a season low, as well as a season low for a Suns opponent.
"We went to the zone, got them out of their rhythm and they never really got back in their rhythm," said Grant Hill, who also scored 19.
The success of the Phoenix bench allowed coach Alvin Gentry to sit starters Stoudemire, Steve Nash and Robin Lopez for the entire second quarter.
"They didn't get in at all in the second [quarter] but they were the first guys off the bench when they were coming out," Gentry said. "That's what makes this team special, how they pull for each other."
The trio returned in the third and picked up where the reserves left off. After Chauncey Billups' 3-pointer pulled the Nuggets within 10 points 35 seconds into the third, the Suns outscored Denver 14-2 over the next 2:35 to open a 73-51 lead, their largest of the night.
The Suns led by no fewer than 11 points the rest of the way.
Frye finished with 16 for the Suns, who won their fifth straight at home and their sixth in seven games overall. Phoenix has won 10 straight at home against the Nuggets dating to 2003-04.
Billups scored 21 points, Anthony had 17 and J.R. Smith added 16 for the Nuggets, who lost for the second time in two days. Denver had not lost consecutive games since dropping three straight from Dec. 25-28.
"If you watched the way we played on the beginning of this trip you'd be happy if we were able to go 2-2," said Nuggets coach George Karl. "We're not happy now but a week from now, hopefully after we win a few home games, we will be happy."
After scoring 33 points in the first quarter, the Nuggets were held to 52 points on 17 of 50 over the final three periods.
"Every time you mention defense and the Suns, people get these sarcastic smiles on their faces," Gentry said. "But we are getting better defensively."
Anthony connected on only two of his final 10 shots from the floor. Denver had a 12-point quarter Nov. 29 in Minnesota. Nuggets forward Chris Anderson limped off the court with 7:33 left in the second quarter with a recurrence of his chronic patella tendinitis in his right knee and did not return. He's listed as day-to-day. The 6-foot-3 Dragic had a pair of dunks during the final minutes of the first half, belly flopping to the floor when his hand slipped after a two-handed stuff on the first and capping a fast break on the second. "Next time I'm going to lay it up," he said.