With the win, the D-backs split the four-game series and now head to Los Angeles, where they will open a three-game series with the Dodgers on Friday night.
Delgado (3-3) started for just the third time this year, and it was his first start since April 10. The decision to go to a six-man rotation was in part to reduce the innings workload on some of Arizona's young pitchers, but it also serves as an avenue for a pitcher like Delgado to show he belongs in the rotation next year.
After allowing nine runs in his first two starts this year, Delgado was shifted to the bullpen, and while he was there, he worked on refining his curveball while also adding a slider to the mix.
"He just really featured all of his pitches," D-backs manager Kirk Gibson said. "He threw any of his pitches in any count."
Said Padres right fielder Seth Smith, who doubled off Delgado in the fourth, "His fastball was good. And once he gets ahead of you, his changeup is a really good pitch. It makes the at-bat difficult."
Delgado did not allow a walk and struck out two while throwing 61 pitches.
"It's a work in progress," catcher Miguel Montero said of Delgado's slider. "It's been getting better and better. Some days you don't have it. But you can tell it's getting better. It's developing pretty good. Today it was outstanding."
When the D-backs acquired Delgado from Atlanta in the Justin Upton trade prior to the 2013 season, it was with the idea of him being a starter, a role that he prefers to pitching out of the 'pen.
"I just tried to stay calm and make quality pitches," Delgado said. "That's what I did tonight. I felt good with the slider and changeup tonight and the location with my fastball. I felt very good today and they played good defense behind me."
Center fielder A.J. Pollock flashed the leather in the third when he appeared to take a home run away from Rene Rivera with a leaping catch at the wall.
Two innings later, Rivera once again got robbed, this time by Aaron Hill, who was playing third base for the first time since 2005. Hill dove and backhanded Rivera's drive down the line.
"Just an all-around good game for us," Gibson said.
Former D-backs ace Ian Kennedy (10-12) was treated rudely by his former mates as they touched him for four runs on 10 hits in 5 1/3 innings.
"I didn't have my put-away pitches," Kennedy said. "I leaked stuff over the plate. And I made some tough pitches and they put the balls in play."
The D-backs capitalized on an error by San Diego third baseman Cory Spangenberg to score three runs in the second and take control of the game.
Hill led off the inning with a single and moved to third on Pollock's double to left.
Didi Gregorius then hit a tapper to Spangenberg, who uncorked a wild throw to first as Hill and Pollock both scored on the play. Ender Inciarte capped the inning with an RBI single.
The D-backs tacked on a run in the third thanks to an RBI single by Montero.