PHOENIX -- When the D-backs were mired in a slide that reached 16 losses in 22 games last week, the team held a meeting, in which the players vowed to have more fun.

Fast forward to Thursday night when fun became a perfect description of Arizona's celebration after Eric Byrnes hit a game-winning, walk-off three-run homer in the ninth to send Arizona to its sixth straight win with a 7-4 victory over the Marlins in front of 18,721 at Chase Field.

The victory moved the D-backs into the sole possession of first place in the NL Wild Card race and gave the young club more reason to believe they are a playoff team.

"I think every day there's more and more guys in here that's starting to believe that," Byrnes said. "If we can have 25 guys have that same feeling, I truly believe we're going to be in the playoffs. Now, we have a long way to go, but I just really think that this is a real good team."

In what Arizona manager Bob Melvin called an odd game, with the D-backs scoring seven runs while banging out only five hits, Byrnes never would have had the chance to play hero if long reliever Dustin Nippert hadn't done the same thing through the middle innings.

Nippert entered with the bases loaded and no outs in the fourth inning and Dan Uggla and Miguel Cabrera due up. He promptly induced a double play and a groundout without allowing a run to score before pitching an additional 2 1/3 scoreless inning in which he only gave up one hit to keep the deficit manageable for Arizona.

"That's the key to the game," Melvin said. "It gets lost in the shuffle as you go forward and Byrnesie's walk-off had something to do with the win, but if 'Nip' doesn't come in and do what he did that inning we're not in this position."

The bullpen continued its dominant trend during this winning streak when Doug Slaten and Tony Pena (5-2) combined for another 2 2/3 scoreless innings. The bullpen has a 0.89 ERA over the past six wins -- the only blemish in the 20 2/3 innings of work was a two-run, one-inning stint from Edgar Gonzalez on Tuesday with the game long decided.

"It's been unbelievable really," Melvin said. "It's phenomenal. It's every one of them too. The bullpen is obviously been the strength here since the break and some offense mixed in as well."

Said Conor Jackson, who tied the game with a pinch-hit two-run homer in the seventh, "They won the game for us without a doubt."

The bullpen bailed out starter Micah Owings for the second straight outing, with Owings giving up four runs on six hits in three-plus innings this time around. His ERA is now 9.52 in five July starts, as he has pitched less than five innings in four of them.

"I can't say enough about them," Owings said. "I'm going to get this 'pen back throughout the season. I'm going to pick them up. They've picked me up plenty of times."

Still, Owings said he felt better than he has in his previous starts despite the rough outing.

Owings' best results came at the plate, where he collected Arizona's only hit before Jackson's blast, hitting a two-run homer to left that marked his first career long ball. Former D-back Byung-Hyun Kim shut down the rest of Arizona's lineup, loaded with lefties, although he has struggled against the D-backs in the past.

Now all of a sudden an Arizona club that appeared to be fading from contention swept its third four-game series of the season with a suddenly hot offense that scored its best three-game total since May after struggling badly at the plate earlier in the month.

"It's amazing just the way things snowball in a good way, and they can snowball in a bad way," Byrnes said. "I think there's guys taking the field believing that we're going to win every night, and when you have that feeling it's a pretty good atmosphere."