Once a top prospect in the Los Angeles Dodgers organization, De La Rosa continues to make progress three years after undergoing Tommy John surgery. There is plenty of upside.
"They came out hot out of the gates," Arizona catcher Tuffy Gosewisch said. "They were ready to go from the first pitch. He gave up a run in the first and I know he gave up a few more but I think he threw the ball well. He really settled down after the fourth and gave up a couple more good innings."
De La Rosa left a ball up and over the plate to Brandon Crawford, who connected for a two-run homer that made it 4-1 in the fourth.
"For us he's tough," Gosewisch said. "He kills us. He makes every hit count. I know he hits eighth for them but he had a lot of quality at-bats. He's a solid hitter."
"We scored one run," manager Chip Hale said. "You're not going to win many games that way. We got beat today, that's the way it goes. Don't make anything bigger out of it than it was."
Joe Panik had three hits and drove in a run as San Francisco snapped an eight-game losing streak. Buster Posey went 2 for 4 with an RBI single on the same night that the Giants received their World Series rings for last year's title.
The Diamondbacks watched the ceremony.
"I just think it's cool for them," Hale said. "We were out there to watch and show our respect. It's not easy to do and it's something that everybody, when we start the season, is aiming for. We're all trying to get there."
Nori Aoki also had two hits, including a leadoff double in the first that led to the Giants' first run and sent them on their way to their first win at home.
Heston (2-1) allowed five hits in 7 2-3 innings. He struck out six and walked one.
"He's got savvy out there," Giants manager Bruce Bochy said. "He's a four-pitch guy with command. That usually works. I know he just pitched against them but he has good stuff and he's made himself into an all-around great pitcher."
De La Rosa (2-1) was charged with four runs, three earned, and nine hits in 6 2-3 innings. He struck out seven and walked two.
"He just left too many pitches up," Hale said. "When he was pitching down he had some success."
Arizona center fielder Ender Inciarte was 0 for 4, ending an eight-game hitting streak.
Diamondbacks: C Gerard Laird (lower back tightness) is eligible to come off the disabled list when Pittsburgh visits Phoenix on Friday.
Giants: RHP Jake Peavy was placed on the 15-day disabled list before the game with a back strain.
RHP Jeremy Hellickson (0-2, 6.55 ERA) starts Sunday's series finale for the Diamondbacks. The 2011 AL Rookie of the Year has lost his first two starts with Arizona.
RHP Tim Hudson (0-1, 2.03 ERA) takes the mound for San Francisco. He is 9-1 with a 2.01 ERA in 13 career starts against the Diamondbacks.