PHOENIX -- Andrew Cashner wasn't satisfied with his pitching Saturday night.
His work at the plate? That was another matter.
"I've been thinking about that my whole life," Cashner said of his home run.
Cashner (7-5) allowed three runs on four hits, walked five and struck out five for his second straight win, both coming during San Diego's 10-game road trip.
"I feel like tonight I wasn't very good," Cashner said. "I walked a lot of guys, but I felt when I got into trouble I made the pitches I needed to."
Cashner walked the bases loaded with one out in the first, but escaped when Martin Prado grounded into a double play. Cashner got another inning-ending double play in the fourth, with runners on first and second.
"I have high expectations for him and maybe a little unfairly because this is his first year as a starting pitcher getting multiple consecutive starts in a rotation," Padres manager Bud Black said. "He made some pitches. But, and this goes back to my expectations of him, when we're up he needs to put the hammer down and finish some innings."
San Diego managed only three hits off Arizona starter Tyler Skaggs (2-3), but took advantage of the rookie left-hander's wildness to open an 8-1 lead after four innings.
"For whatever reason, he had no command of his fastball," Arizona manager Kirk Gibson said. "He was trying to throw the ball in and couldn't get it in there. He is obviously struggling. He gets guys on base and puts some pressure on. You can see by his mannerisms he feels it a little bit."
After the game, Skaggs was optioned back to Triple-A Reno, where he is 6-5.
"Up here you need to throw a fastball, you need to throw it for strikes and work it in and out," Skaggs said. "I haven't been doing that. I'm only 22, so I have a lot more starts ahead of me."
With the game tied 1-1, Skaggs retired the first two batters he faced in the third. But he walked Denorfia, hit Headley with a pitch, walked Quentin to load the bases and then walked Jesus Guzman to force in Denorfia.
Alonso followed with a bases-clearing double into the right-field corner to give the Padres a 5-1 lead.
"I had to take the first pitch because he was walking a lot of guys and I wanted to see if he could throw a strike," Alonso said. "As soon as he threw the strike I knew the at-bat was on, so I was just trying to get something over the plate and try to hit it."
In the fourth, Skaggs walked Cashner with one out before giving up a two-run, two-out home run to Denorfia to make it 7-1.
Tony Sipp came on in relief, but Headley drove his first pitch into the left-field stands to stretch the lead to 8-1.
"We knew that Skaggs could be a little variable with his command and control," Black said. "I thought our guys, especially in the third and the fourth innings, did a good job of laying off some pitches that were borderline and making him throw strikes. Out of the chute he looked pretty good, but he wobbled a little bit and our guys were patient and it really paid off. This was a game that was won because we let the other guy falter."
Skaggs allowed seven runs on three hits and five walks, hit a batter and struck out five over a career-worst 3 2/3 innings.
"He wants to be so perfect," Montero said. "He put too much pressure on himself. That is not going to help him. You have to relax a little bit. You have to make one pitch at a time and that is when you are going to get out of a jam. But if you try to make just one pitch and get three outs it is tough to do."
Goldschmidt's one-out homer in the fifth, his 23rd, pulled Arizona within 8-3.
San Diego took a 1-0 lead in the first when Denorfia walked and scored on Quentin's two-out double.
Arizona tied the game in the second on Montero's third home run in his past seven games.
The Diamondbacks did not announce the corresponding move to replace Skaggs. ... Alonso has nine RBIs in nine games since the All-Star Break. ... Skaggs had issued 10 total walks in 35 innings across his last six starts. ... Denorfia's nine home runs against Arizona are the most among active Padres. ... Denorfia and Headley were the fourth set of Padres to hit consecutive home runs this season. Nick Hundley and Will Venable hit back-to-back homers July 15 against San Francisco. ... Montero had missed the Diamondbacks' past three games with a stiff back. ... Arizona LHP Patrick Corbin (12-1, 2.31 ERA) will look to remain unbeaten at home when he takes on RHP Tyson Ross (1-4, 3.35) in the series finale. Corbin is 8-0 at Chase Field, the second-most home wins in the majors. Ross snapped a 12-game losing streak when he held the Brewers to two hits and two walks in the Padres' 6-2 win.