The play happened with the Padres already leading 3-2, and it seemed to energize the Padres when they batted in the sixth.
"When you get one, and then you get two it's even better," Alonso said of the big double play. "After we came back in from that inning, we were very excited for the play and we just knew we needed to score more runs and we did that.
"We just feel that we play well here [in Phoenix]," Alonso said. "It's a good place to play."
Two walks sandwiching an out brought up Quentin, who got drilled in the back by an Ian Kennedy pitch to load the bases. Grandal walked to drive in a run and Alonso singled to right for two more, Quentin hustling to get around Montero's tag at home.
Quentin set a Padres single-season record for times hit by a pitch, 16. The previous record belonged to Kevin Kouzmanoff, who was hit 15 times in 2008.
The Padres went up 6-2 and added three more runs for their sixth straight win overall, tying a season high. Left-hander Clayton Richard pitched eight innings for the win to improve to 11-12.
"Defensively we were terrific. They really kept me in the game," Richard said. "A couple of plays that Chase made, I really don't think I would have lasted that long if he didn't make those plays."
Padres manager Bud Black never considered allowing Richard to go for the complete game, given the high innings total (184) for Richard this season.
"He prides himself on his endurance, his stamina and his conditioning," Black said of Richard.
Kennedy, 6-0 against San Diego in nine previous career starts, didn't have that magic Saturday. He lasted 5 1/3 innings and allowed six earned runs on four hits, with some uncharacteristic wildness in walking four.
Justin Upton's first inside-the park home run of his career gave the D-backs a 2-1 lead in the second inning. He lined the first pitch he saw from Richard off the base of the wall in center field, and the carom rolled back toward left field as Upton sprinted around the bases. The Padres never had a chance to try and throw him out.
Headley's sore wrist, which he hurt going up for a line drive on defense in Friday's game, apparently wasn't bothering him too much. Headley ripped the first pitch - a fastball he said he was looking for -- from Kennedy over the right-field fence near the corner for a solo home run in the first inning to give the Padres a 1-0 lead.
The Padres added single runs in the fourth and fifth innings, with Quentin hitting his 14th home run and Alonso his seventh of the season.
"Just not trying to do too much," Alonso, who has hit in 19 of his last 26 games since July 27, said. "I feel like this whole year, it's been a learning process. And early in the year, I was trying to do so much. Trying to hit, trying to drive the ball every time. You don't really need to do that. All you need to do is put the ball in play."
Alonso went 2-for-3 with three runs batted in. Upton, celebrating his 25th birthday, had two hits for the D-backs (64-63), who failed to gain ground on NL West foes San Francisco and Los Angeles above them in the standings.
"We had a couple opportunities to get a couple runs, but we didn't do that," D-backs manager Kirk Gibson said. "They out-executed us in every aspect of the game, that was it. They were being very productive with their at-bats, we weren't."
The Padres (58-70) go for a series sweep Sunday. They have three games remaining to play in Phoenix this season, Sept. 18-20.