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PHOENIX -- The foundation of the Arizona Diamondbacks' success this season has come from its ability to get production throughout the lineup, so it was no surprise when two of the team's newest players came through against the San Diego Padres.

Ian Kennedy? He's been doing this all season.

Kennedy pitched seven effective innings to become the National League's first 17-game winner, Collin Cowgill and Aaron Hill provided the offense and the Diamondbacks beat the Padres 6-1 on Sunday for their sixth straight victory.

"Everybody speculated when I named him Opening Day starter and he's lived up to it," Diamondbacks manager Kirk Gibson said of Kennedy. "He's been huge."

Cowgill, who made his major league debut in late July, had been struggling the past couple weeks, fighting himself and his swing. More relaxed after a chat with a sports psychologist, the rookie had his best game in the majors, hitting a solo homer off Cory Luebke (5-7) in the second inning and a run-scoring double off Erik Hamren in the eighth to finish off a four-hit day.

Hill, acquired in a trade with the Toronto Blue Jays on Tuesday, had his first homer with Arizona and added an RBI single, finishing with three hits and three RBIs.

Kennedy (17-4) did what he always seems to, churning out another quality start to win for the ninth time in 10 outings. The right-hander settled in after giving up a homer to Orlando Hudson in the second inning, allowing one run or fewer for the 13th time this season to complete the three-game sweep.

The victory, combined with the San Francisco Giants' extra-inning loss to the Houston Astros, puts the Diamondbacks four games up in the NL West with 28 games left.

"It's unbelievable; they never doubt themselves for one second," Cowgill said. "You find that contagious, you feed off that. When a guy's struggling, there's somebody there to pick them up."

Coming off a six-game losing streak that threatened to derail the season, Arizona has rallied behind its starting pitching.

Kennedy has been on a roll, allowing no more than three runs in his previous nine starts while moving toward the top of the NL Cy Young favorites list. He didn't like the way he was locating his fastball the last time out but still tossed seven scoreless innings with eight strikeouts in a 2-0 win over the Washington Nationals on Tuesday.

Kennedy had some shaky moments early against the Padres, too. Jesus Guzman nearly hit one out in the first inning and Hudson did do it in the second, leading off with a shot that landed on the pool deck in right-center.

Kennedy fell into a groove after that, though, scattering four hits over the next five innings. He was lifted for a pinch-hitter in the seventh after allowing six hits and striking out seven.

Arizona has allowed two runs or fewer in six straight wins for the first time since setting a club record of eight straight in 2002.

"This year their pitching is really come on," Padres manager Bud Black said after his team's fourth straight loss. "The two guys at the top of the rotation, Kennedy and (Daniel) Hudson have come into their own. They have a couple of years under their belt and they are pitching with a lot of confidence and good stuff."

Arizona's offense gave Kennedy plenty of support.

Cowgill hit his first career homer with an inside-out swing that sent the ball just over the wall in right.

Hill, who came over with shortstop John McDonald from Toronto in a trade for Kelly Johnson, hit his first homer with the Diamondbacks in the third inning, a two-run shot off Luebke that made it 3-1.

Luebke, 2-0 with a 1.88 ERA his previous four starts, didn't give up much after that, leaving with one out in the sixth after allowing three runs on six hits. Good, just not good enough.

"I couldn't keep the ball in the park today and that ended up being the difference. That is just a matter of getting ahead too. Both of these guys I fell behind and tried to get back into the count and left fastballs over the plate.

Arizona broke it open with three runs in the eighth inning.

Cowgill knocked one in with an RBI double to right, Hamren walked Ryan Roberts with the bases loaded and Hill finished it off with a run-scoring infield single to push the Diamondbacks a step closer toward a division title after consecutive 90-loss seasons.

"We weren't playing well before this, so we're kind of making up for it," Kennedy said. "It's nice to do this at home, go on this streak against guys in our division. It's a lot of fun right now."

Game notes

Padres center fielder Cameron Maybin missed his second straight game with a sore right wrist. ... Kennedy is 7-0 with a 1.98 ERA in 11 starts against the NL West this season. ... Arizona moves on to face the Colorado Rockies in a three-game series at Chase Field, starting Monday, with right-hander Daniel Hudson pitching the opener against Alex White. Hudson was on the verge of his first shutout against the Nationals on Wednesday before allowing two runs in the ninth inning of the 4-2 win. ... San Diego wraps up an eight-game road trip with three against the Los Angeles Dodgers, starting Monday. Right-hander Mat Latos, who has a 2.45 ERA in three August starts, will face Los Angeles All-Star Clayton Kershaw in the opener.