Before this season, the San Diego Padres had never recorded a sweep in Arizona. Now they are on the verge of their second one in 2012.
The Padres seek a seventh straight win overall and sixth in a row against the Diamondbacks on Sunday.
San Diego has rebounded from a five-game losing streak with six consecutive wins, including a 9-3 victory Saturday. Yonder Alonso hit one of his team's three home runs and added a two-run single to back eight innings from Clayton Richard.
Chase Headley hit his major league-high 10th home this month and Carlos Quentin went deep for the 14th time this season.
The win was the Padres' fifth straight over the Diamondbacks, with all five coming at Chase Field following a three-game sweep in early July.
Prior to that series, San Diego (58-70), which has outscored the Diamondbacks 37-16 during the current streak, had never swept a series in Arizona.
"We just feel that we play well here," Alonso, who is 8 for his last 16 at Chase Field, told the Padres' official website. "It's a good place to play."
A victory in the finale would give San Diego its first seven-game streak since an eight-game run from April 16-24, 2010.
While the Padres are playing well in Phoenix, the Diamondbacks (64-63) are struggling there, losing nine of 14 at home. They split a four-game series against Miami earlier this week and are averaging 2.8 runs and hitting .213 on this 10-game homestand.
Bouncing back could be difficult if Edinson Volquez (8-9, 4.18 ERA) is able to build off one of his better starts in a month.
Volquez gave up one run and five hits over 6 2-3 innings and matched a season high with 10 strikeouts in a 3-1 victory over Pittsburgh on Monday.
The right-hander had a 13.83 ERA over his previous four starts, spanning 13 2-3 innings.
"About time," Volquez said. "It's a lot of work with my pitching coach (Darren Balsley). I was under control with my mechanics, my delivery was better, my fastball command was better. Everything was better."
Volquez doesn't have a decision in two starts against the Diamondbacks this year - both Padres losses. He's allowed two runs in each outing, going 13 innings.
Chris Young and Miguel Montero are a combined 2 for 23 with nine strikeouts against Volquez.
Arizona planned to counter with Joe Saunders, but instead traded him to Baltimore earlier Sunday for reliever Matt Lindstrom and cash considerations or a player to be named later.
A replacement wasn't immediately announced, but Trevor Cahill (9-10, 3.86) could go on full rest. The right-hander has posted a 1.29 ERA in three starts against the Padres this year despite walking 12 over 21 innings.
Cahill, though, has a 5.79 ERA in four home starts since the All-Star break.