(SportsNetwork.com) - Rubby De La Rosa has been able to lean on his offense a bit to win his first two starts of the season.

Chris Heston could have a similar 2-0 record if not for a lack of support last time out.

The hurlers square off on Saturday night when De La Rosa's Arizona Diamondbacks play the third contest of a four-game set with the San Francisco Giants, as they try to extend the champs lengthy losing streak.

De La Rosa escaped with a season-debuting win over the Giants on April 7, getting a favorable 7-6 decision despite allowing six runs over 5 1/3 innings. The right-hander then did just enough to beat San Diego on Monday, yielding three runs on six hits with five strikeouts in an 8-4 win.

The 26-year-old is 1-0 with an 8.18 earned run average in three games (2 starts) versus the Giants.

Pressed into the starting rotation due to Matt Cain's injury, Heston has split his first two starts with the Giants and looks to post a third solid outing tonight for San Francisco.

Heston picked up the first win of his career when he opened the season with a 5-2 victory over Arizona on April 8. The 27-year-old righty yielded a pair of unearned runs over six innings, working around three hits and two walks while striking out five.

Heston then made the third start of his career on Monday versus Colorado and suffered a 2-0 loss. He yielded two runs -- one earned -- on seven hits and another two walks while again striking out five.

San Francisco went 0-for-7 with runners in scoring position in the game.

Things weren't any better for the Giants' offense in last night's series opener as the club was blanked 9-0 for an eighth straight loss.

Jake Peavy gave up four runs on eight hits in just 3 2/3 frames for the Giants as he continues to deal with a nagging back injury.

"We're in a tough rut," San Francisco manager Bruce Bochy said. "Right now, we aren't playing very well."

Josh Collmenter tossed a four-hit shutout for the Diamondbacks, walking one and striking out a pair. He also had three hits and drove in a run at the plate.

"Not only the pitching, but the bat was incredible," Diamondbacks manager Chip Hale said of Collmenter. "Just an overall great game and just what we needed."

David Peralta went 3-for-5 with two doubles, two RBI and a run scored, A.J. Pollock had four hits and an RBI and Jake Lamb tripled and drove in two runs for the Diamondbacks, who had lost three of four coming into this series.

The Giants have won 11 of their past 16 versus the Diamondbacks.