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Eric Stults had baffled the Arizona Diamondbacks the last time he faced them. In fact, the San Diego right-hander hadn't lost a game since June 3.

But he and his teammates weren't quite good enough Tuesday night against Diamondbacks right-hander Ian Kennedy, who got stronger as the night went on.

Arizona's 3-2 victory marked the first time the Padres had lost at Chase Field this season. They had swept their first two three-game series in the desert.

Stults (6-3) had gone 5-0 with a 2.08 ERA in his seven starts since rejoining the rotation on Aug. 6. The last time he faced Arizona, on the same field on Aug. 24, he had blanked the Diamondbacks on three hits over seven innings.

This time, he said, "They had a little different approach."

"They were sitting off-speed tonight, especially early in the count," Stults said. "The first two times I faced them I was able to get ahead early (because) they were more a little more aggressive early in the count."

Kennedy, meanwhile, survived a 30-pitch first inning to go eight, allowing a run and seven hits. He struck out six and walked two, one intentionally.

"The way he threw the last four innings was more indicative of how he threw the ball last year, when he won 20 (actually 21) games," Padres manager Bud Black said. "A good fastball at the top of the zone and had some carry to it. Early in the game he threw a lot of off-speed pitches and not many fastballs. It was a classic case of him getting better as the game went on."

Kennedy (14-11) is 8-3 in his last 12 starts.

"He's aggressive now. You see his velocity up. In the last inning he was throwing 90-91 (mph)," said catcher Miguel Montero, who drove in two runs with two doubles. "And his command, his command on his secondary stuff, he's been able to throw it for a strike. That's big. It's not like they're just sitting on fastball because he can't locate a breaking ball. Right now he can throw every pitch for a strike."

Stults gave up three runs and five hits in six innings.

"Stultsy did fine," Black said, "a little bit of an elevated pitch count, which is something he hasn't done. He has been very efficient and throwing the ball well. He gave up three runs and I am sure he wishes he had a couple of pitches back, some breaking balls that stayed up in the zone. He threw well enough to keep us in the game. Their guy just outpitched, bottom line. "

The Padres got a run in the ninth inning after Chris Denorfia singled and reached third when the ball got past Adam Eaton in center field for a two-base error. Will Venable's sacrifice fly brought Denorfia home but J.J. Putz retired Jesus Guzman and pinch-hitter Mark Kotsay to earn his 30th save in 35 opportunities.

Kennedy, pitching on an extra day's rest, struck out seven, two in his final inning. He walked two, one intentionally. His 121 pitches were one shy of his season high.

Stults struck out six, walked three and hit a batter.

Arizona center fielder Chris Young, in the lineup for the first time since Sept. 3, aggravated his right quadriceps injury running down a fly ball for the first out of the game.

When he left the game, Eaton shifted from left to center, and Gerardo Parra came in to play left.

After the substitution, Logan Forsythe singled and Chase Headley walked, then Yasmani Grandal singled off the glove of Kennedy to load the bases. Yonder Alonso hit a sacrifice fly to left. Parra's throw reached home ahead of the runner, but Forsythe slid under the tag of the catcher Montero, who did not block the plate.

The Diamondbacks responded with two runs in the bottom of the first. Eaton led off with a walk, stole second, and, with two outs, scored on Paul Goldschmidt's single. Goldschmidt scored from first when Montero doubled to right.

Arizona added a run in the fifth when Justin Upton drew a one-out walk and raced home from first on Montero's double high off the wall in center.

Notes: In their two three-game sweeps in Arizona, the Padres outscored the Diamondbacks 42-20. ... Arizona's top minor league club, the Reno Aces, won the Triple-A championship 10-3 over Pawtucket on Tuesday night. Two other D-backs minor league teams, Double-A Mobile and Rookie League Missoula, won their league titles. ... In Game 2 of the series on Wednesday night, the Diamondbacks go with RHP Trevor Cahill (11-11, 3.92 ERA) against the Padres' RHP Edinson Volquez (10-10, 4.24). ... Phoenix Suns guard Goran Dragic will throw out the first pitch at Wednesday night's game.