SAN DIEGO -- In Jhoulys Chacin's first start as a Padre on Opening Day last Tuesday, the right-hander gave up nine runs on eight hits and two walks and didn't make it out of the fourth inning.

"I knew I had to pitch better tonight, to beat Bumgarner you can't make mistakes," said Chacin Saturday night after he outdueled Giants ace Madison Bumgarner in a 2-1 Padres win at Petco Park.

Chacin (1-1) allowed three hits and a walk with five strikeouts in 6 2/3 scoreless innings.

"Chacin's mix was outstanding tonight," said manager Andy Green after the Padres' second straight win over the struggling Giants.

"The fastball, the slider. And he and (catcher Austin) Hedges were working well together."

"I'm really happy," said Chacin. "I know what I can do. The last game, I wasn't making good pitches. Tonight I had better command of my fastball. When I have good command of the fastball, the breaking balls are better."

"You have to give Chacin credit," said Giants right fielder Hunter Pence. "He was good today."

Three Padres combined on a five-hitter.

Left-handed reliever Brad Hand followed Chacin and retired all four Giants he faced with one strikeout.

Back-to-back, two-out singles by Buster Posey and Brandon Crawford off left-handed Padres reliever Ryan Buchter put the Giants on the board in the ninth. But Buchter retired Eduardo Nunez on a high fly to left to end the game to pick up his first save of the season -- and the second of his major league career.

Meanwhile, Bumgarner (0-1) went the distance for the Giants, allowing two runs on six hits and two walks with five strikeouts in eight innings. Bumgarner retired the last 10 Padres he faced.

Bumgarner's downfall was the three rookies in the Padres' starting lineup -- outfielders Manuel Margot and Hunter Renfroe and surprise starting shortstop Allen Cordoba, a Rule 5 acquisition last December who had never before started a game above Rookie ball.

They combined for five straight hits off Bumgarner and collectively had a hand in both Padres runs -- one in each of the game's first two innings.

Margot led the way with doubles in his first two at-bats with a run scored and an RBI. Renfroe had two hits, including an RBI double.

But it was Cordoba who scored the eventual winning run after leading off the second with his first major league hit.

"It's great, especially to get that first hit off someone like Bumgarner," said Cordoba, who had no idea he was starting until he got to the Padres clubhouse Saturday.

"I thought I'd be on the bench," said Cordoba, one of three Rule 5 players on the Padres' 25-man roster. "I came into the clubhouse and saw my name in the lineup."

As Cordoba was approaching the plate, Green said he glanced up at the scoreboard "and saw they were showing Cordoba's Appalachian League statistics from last year."

Before the game, Green joked about starting the 21-year-old Cordoba against one of the game's top pitchers.

"Part of the thought process of putting a young guy like Allen Cordoba in there today ... Cordoba doesn't know any better, just swing the bat and go play. I hope the fact that Bumgarner doesn't know Allen Cordoba at all plays in our favor a little bit."

It did.

Cordoba grounded a single to left leading off the second, advanced to second on a sacrifice bunt by Chacin and scored on Margot's double in as many innings -- a shot down the third-base line.

In the first, Margot opened the game with a hustle double on a grounder to short left-center, moved to third on an infield out by Wil Myers and scored on a double by right fielder Renfroe.

Bumgarner said he battled through the first two innings.

"I'm having trouble getting it going," he said. "I didn't start the way I wanted to, crisp and sharp. So I was battling there. Really, it was a battle the whole game. Some things just didn't go our way.

"They tipped their hand early and we adjusted and I got to stay in there a little longer and give us a chance to win. That was just a tough day for us."

NOTES: CF Denard Span returned to the Giants' starting lineup after missing three starts with a sore left hip. ... Padres RHP Carter Capps pitched a simulated game and is scheduled to start a rehab assignment with Class A Lake Elsinore on Monday. ... In his first six at-bats against Giants ace LHP Madison Bumgarner, Padres rookie RF Hunter Renfroe has four hits, including two doubles and a homer. ... SS Allen Cordoba, a Rule 5 acquisition by the Padres in December, got his first major league hit with a second-inning single off Bumgarner.