San Diego has won five consecutive games, one short of its season-best streak, and also has taken all four meetings at Chase Field this season.
Clayton Richard takes on the task of keeping those runs intact, as the left-hander matches up against D-backs righty Ian Kennedy.
Richard (10-12, 3.73 ERA) has been a stable force in the Padres' rotation, leading the team with 15 quality starts and sitting near the top of the National League with 176 innings pitched. He has worked at least six frames in 21 of 25 starts.
Richard has compiled a 2.02 ERA over his last five outings, including on Sunday against the Giants. San Francisco managed only an unearned run on five hits in eight innings.
"[Richard] has been great," Padres center fielder Cameron Maybin said. "He and [Edinson] Volquez have been two of the guys that have been in the rotation all year, and Clayton has been amazing. He continues to go out and pound the strike zone and get ahead of guys. He's just fearless. You love playing behind a guy like that."
Kennedy (11-10, 4.24 ERA) also picked up a win on Sunday, limiting the Astros to a run on five hits in six innings. He struck out seven but also walked a season-high five and had to strand runners in all but one inning.
"That's what I really take pride in -- not walking too many guys," Kennedy said. "Thankfully, we hit well today. I put a lot of hitters in hitters' counts and just luckily got out of it."
Padres: Thayer goes on paternity leave
Right-hander Dale Thayer, one of the Padres' options at closer with Huston Street on the disabled list, was placed on the Major League paternity list. His wife, Lisa, gave birth to the couple's third daughter early on Friday morning.
San Diego recalled left-hander Josh Spence from Triple-A Tucson to fill Thayer's roster spot. In 11 games this season, Spence has a 4.35 ERA, 10 strikeouts and five walks.
Thayer is second on the team with seven saves, including two since Street went down. Rookie southpaw Tom Layne closed out the team's win on Wednesday, with two left-handers due up in the inning and Thayer having pitched two days in a row.
Street, recovering from a strained left calf, played catch on Friday as he heads toward either a Minor League rehab assignment or a simulated game.
D-backs: Bad back keeps Bloomquist sidelined
Infielder Willie Bloomquist was eligible to be activated from the 15-day disabled list on Friday, but the club elected to keep him there after the 34-year-old felt stiffness in his back while playing in a Minor League rehab game the day before.
"He didn't feel that good last night when he played," manager Kirk Gibson said. "It's not bad like it was, but he's not stiff-free. I'm not going to rush him back when he's played a minimal amount. Just didn't feel good after that."
Bloomquist's DL stint is retroactive to Aug. 9. He went 1-for-3 with a triple and three RBIs for the D-backs' Arizona Rookie League affiliate on Thursday.
A nagging left hamstring injury held right fielder Justin Upton out of the lineup for the third straight game on Friday, although he made it through conditioning drills without a problem earlier in the day.
"We're going to give him another day," Gibson said. "I knew what he did, I saw it happen, I think there needs to be more comfort."
Richard's ERA is 4.63 on the road, nearly two runs higher than his mark at Petco Park.
Both pitchers have started twice this season against Saturday's opponent. Richard has allowed three runs in 15 1/3 innings, while Kennedy has allowed five runs in 13 innings.