SAN DIEGO -- The Arizona Diamondbacks were relieved just to win, no matter how they achieved it.
"A win is a win," Arizona manager Bob Melvin said. "They all count the same. Although not exactly in the fashion we'd like, especially the way it started out."
The Diamondbacks, who trailed San Diego by one percentage point coming into the game, held on after taking an 8-0 lead in the seventh to avoid the four-game sweep.
"It's huge," Reynolds said about the win in the series finale. "We came in here today and didn't really think about the past three days. We knew we were still tied for first and nobody thought we would be in this position."
Reynolds hit a two-run homer an estimated 451 feet into the second deck in left field off Chris Young (9-5) in the second inning. Reynolds, who had three hits, then capped a four-run fifth inning with a three-run double off Cla Meredith.
"That was an unbelievable game for (Reynolds)," Melvin said. "He had the at-bat of the game against Meredith."
Arizona moved into first place, one game ahead of San Diego. The Padres' lead in the wild-card race was cut to two games over Philadelphia, which beat New York earlier in the day.
Doug Davis (12-11) allowed three runs on four hits over 6 2/3 innings to improve to 7-1 in 10 starts since the All-Star break. Davis struck out seven and walked two as the Diamondbacks won for the ninth time in his 10 second-half starts.
Jose Valverde gave up a solo homer to Milton Bradley in the ninth before finishing up for his major league-leading 41st save.
"That was a nail-bitter but we came through and won the game," Davis said.
Young had control problems in his first start since leaving his Aug. 21 outing at New York after five innings due to lower back pain. Young, who missed his next scheduled start Sunday at Philadelphia, matched his career high with six walks. The 6-foot-10 right-hander also hit a batter as he allowed five runs and two hits with three strikeouts in 4 1/3 innings.
"It's a little tight right now," Young said about his back. "When I was on the mound, I didn't feel it, didn't think about it. It was rusty, that's it."
"The first six innings I was getting ahead and make them hit the pitch I wanted them to hit," Davis said. "In the seventh, I fell behind a lot. That's why I got in trouble in that inning."
The Padres scored three more in the eighth to pull to 8-6. Kouzmanoff and Josh Bard had consecutive run-scoring singles, and Stansberry's added an RBI infield single.
"We battled back and had the opportunity to win," Giles said. "That's all you can really ask for."
Reynolds put the Diamondbacks ahead in the second inning after Drew got on base with a one-out walk. With two outs, Reynolds hit Young's 88 mph fastball deep into the second deck in left field for the third-longest homer in Petco Park's four-year history.
Young's control problems continued in the fifth. With one out, he walked Orlando Hudson, hit Eric Byrnes with a pitch and loaded the bases with a walk to Clark. Joe Thatcher relieved and walked Drew to force in one run. Meredith then came on and Reynolds cleared the bases one out later with a double over the head of right fielder Giles.
Young's ERA rose from 2.12 to 2.38 as he surrendered the major-league ERA lead to teammate Jake Peavy (2.18). The five runs he allowed equaled the number of runs Young has given up at home this season in 10 previous starts. His ERA at Petco Park went from 0.66 to 1.24.
- Reynolds' homer was the first allowed by Young at home since Sept. 22, a stretch of 69 2/3 innings. It was also only the sixth home run allowed by Young this season.
- The only time the Padres have swept a four-game series from Arizona came in April of the Diamondbacks' inaugural season of 1998.
- Young is 0-2 with a 5.40 ERA in his last four starts.