The D'Backs won their 15th straight home game on Saturday, as Lyle Overbay drew a bases-loaded walk in the bottom of the 10th inning helping Arizona rally for a 6-5 win.
Overbay and Chris Young had hit back-to-back homers an inning earlier to send the game into extras.
"It just seems like it's a different person every night," said Overbay. "We got down early. They shut us down, we got to the ninth and were able to tie it up. We got to the 10th, great at bats, and we were able to put one across."
David Hernandez (4-3) stranded two runners in the top of the 10th to earn the win for the Diamondbacks, who lead the NL West by 9 1/2 games. Arizona's magic number to win its first division title since 2007 is now down to eight.
Joe Thatcher issued the decisive walk in the home 10th after Brad Brach (0-1) allowed the Diamondbacks to load the bases.
James Darnell hit his first major league home run for the Padres, who have lost 14 of their last 16 games.
Today, Arizona will hand the ball to righty Josh Collmenter, who is 9-8 with a 3.10 ERA. Collmenter did not get a decision on Tuesday in Colorado, but pitched well, as he allowed a run and five hits in 6 1/3 innings of an 8-3 loss.
"Josh was awesome," Arizona manager Kirk Gibson said. "He threw a great game within the elements and everything, and had them totally off guard."
Collmenter tossed 5 1/3 scoreless innings to beat the Padres the last time he faced them in his only other start against them.
San Diego will counter with lefty Wade LeBlanc, who has lost his last three starts. LeBlanc lost to San Francisco on Tuesday, as he surrendered four runs and eight hits in five innings, dropping him to 2-5 on the year to go along with a 5.33 ERA.
LeBlanc has faced the D'Backs six times and is 1-2 against them with a 5.76 ERA. He was also on the wrong end of Collmenter's gem back on August 26.
Arizona has won 10 of its 14 meetings with the Padres this season.