PHOENIX -- Give Doug Davis all the credit in the world for the D-backs' 9-1 win over the Padres on Tuesday night, because he tossed a gem.

Just make sure you also throw some Tony Clark's way, because the veteran first baseman's two-run homer in the first inning set the tone for a much-needed win that pulled the D-backs into a virtual tie with the Padres atop the NL West.

The D-backs lost three of four to the Padres last week at PETCO Park and they dropped the opener of this series on Monday afternoon. So with San Diego ace Jake Peavy scheduled to start on short rest Wednesday, the pressure was on Arizona.

"Early on we needed some momentum going forward -- score some runs early on and get a lead," D-backs manager Bob Melvin said.

The first two hitters in the Arizona first inning coaxed walks from Chris Young, but then Eric Byrnes grounded into a double play that seemed to take the wind out of the D-backs sails especially since they were convinced that Byrnes had beaten the throw to first.

That brought Clark up to the plate. The veteran got the start because he has owned Young in the past. Coming into the game he was 3-for-7 against the right-hander and all three of the hits were homers.

After his first at-bat of the game he was 4-for-8 with four homers as he launched a 2-1 offering 438 feet to dead center to give Arizona a 2-0 lead.

"We obviously had a different opinion on that play," Melvin said of the double play call. "But Tony just picks us up. The momentum all of a sudden shifts to them and then after Tony's homer it shifts right back into our dugout."

The D-backs increased their lead to 5-0 in the third when Byrnes hit a three-run homer off Young.

That allowed Davis to relax, but it's not like he needs much help these days. The left-hander has won eight of his last nine decisions and his timing couldn't have been better with the streak starting in early July when the D-backs first learned Randy Johnson would miss the rest of the season.

"He's a tougher guy than I originally thought and saw from the other side," Melvin said. "He's got a lot of grind in him and I didn't know that coming in. He competes really hard out there and is always very, very prepared."

Davis (13-11) had command of all his pitches and mixed them nicely. He's known for throwing his cutter inside to righties when he's in a jam so Tuesday he threw cutters on the outside corner and he used his changeup to get ground balls and a couple of popups.

The Padres threatened with runners on first and second in the third inning and first and third in the fourth, but in both instances Davis was able to induce a double play grounder.

"Whenever a pitcher gets in trouble your best friend is a double play," he said. "I got key double plays today and the defense played awesome behind me."

It was Davis' second straight win in as many starts against the Padres as he beat Young last week for the D-backs' lone win of that series.

"I didn't see anything different as far as pitch selection," San Diego manager Bud Black said. "He might have thrown a few more curveballs. But it didn't look like he's changed his game plan."

The D-backs didn't alter their approach to Young, who has pitched well against the rest of the NL, but is 0-3 with a 7.32 ERA in four starts against Arizona.

Only when it was over did Davis allow himself to reflect on the importance of the game, which sets up a rubber match for Wednesday, the final regular-season meeting between the two teams.

"We've been pretty evenly matched and everybody's talking about how these guys were burying us," Melvin said referring to the fact that the D-backs lead the season series 9-8. "We had our way with them earlier and then as of late they've had their way with us. They're bringing Jake back on three days so it's going to be a tough game for us tomorrow but I think after today we feel good about going into tomorrow."