The Pirates have won five road series already, one more than they did all of last year. They've got 11 road wins -- last year they didn't get their 11th until June 28.
The Pirates were the worst team in the majors last year at 57-105, including 17-64 on the road. It was their 18th straight losing season.
"There was change over the winter, and I think by the time spring training came, I think they felt, 'We've got a new start,'" new manager Clint Hurdle said. "Lessons needed to be learned from taking the whupping that they took last year. In life you're going to take some whuppings. When you learn from them, they can be productive. If you're just taking whuppings and not learning anything, that's when it gets painful."
The Padres, meanwhile, are a major league-worst 5-13 at home.
Correia (5-2), has won all five road starts this year, with a 1.55 ERA. He allowed two runs and five hits in six-plus innings, struck out three and walked two.
The Padres didn't bring back Correia after he went 10-10 with a 5.40 ERA last year, when he lost his spot in the rotation in September. The year before, he was San Diego's most consistent starter, going 12-11 with a 3.91 ERA in 33 starts.
"He's been a lot of the reason why we've had some success on the road," Hurdle said. "You like a guy to jump out and be the lead dog in the dogsled and that's what he's done in the rotation. He's jumped out. He's setting the bar and the guys are following."
Correia downplayed pitching against his hometown team.
"It wasn't really a big deal for me," he said. "I've pitched here a lot over the years and it's just kind of been there, done that now. I didn't really put a lot of significance into it. It was just another start and I just wanted to go out there and win a game."
Correia said he understood why the Padres didn't have him back.
"I was fine with it. I mean, they had a good pitching staff. That's kind of what happened in San Francisco. And that's nice. I got to come over and play with some guys and see some really good pitchers maturing," Correia said. "They didn't really need me anymore. That's how baseball is. I'm just glad I got the experience to be able to play in my hometown for a couple of seasons."
Pittsburgh benefited from two Padres errors in the third to score six unearned runs on just three hits against lefty Clayton Richard (1-3).
After Correia struck out, Andrew McCutchen singled and was safe on Xavier Paul's dribbler in front of the plate when catcher Nick Hundley threw wide of second for an error. The Pirates loaded the bases when third baseman Chase Headley couldn't get the handle on Matt Diaz's grounder for another error. Neil Walker hit a two-run single before Steve Pearce walked to load the bases again.
Doumit unloaded them with a grand slam to left on a full-count for a 7-0 lead. It was his third career grand slam and second homer of the season.
Doumit was looking for a pitch to elevate in spacious Petco Park to at least bring in a run.
"I know I hit mine very well, and at the bare minimum I was going to get a double out of it. It was one of those things where luck was on my side today," Doumit said.
"Those situations, you have to pick up your teammates," Richard said. "But these things happen. Errors are made and that's part of the game. It's disappointing not to make some pitches to get us out of it. That's probably the thing that hurt most."
Walker drew a leadoff walk in the second and eventually scored on a force play.
Correia was chased in the seventh when Brad Hawpe doubled in Cameron Maybin, aboard on a leadoff single. The Padres scored their first run in the fourth when Will Venable hit a leadoff triple and came in on Ryan Ludwick's groundout.
Hawpe hit his first homer of the year, a solo shot to center leading off the ninth off Jose Veras. It went an estimated 435 feet. With one out, Eric Patterson hit a solo shot to right, his second in as many games.
Richard is winless in six starts since a victory at St. Louis on April 2, the second game of the season. He allowed seven runs, one earned, on four hits in five innings. He struck out four and walked three.
Correia is the first Pirates pitcher to win his first five road starts since Don Robinson, who won his first seven in 1982. ... The Padres placed second baseman Orlando Hudson on the 15-day DL with a strained right hamstring and selected infielder Logan Forsythe from Triple-A Tucson. Hudson was hurt in Tuesday night's 6-5 win. Forsythe made his big league debut, grounding out while pinch-hitting for Richard. ... The Padres also transferred left-handed reliever Joe Thatcher from the 15-day to the 60-day DL.