SAN FRANCISCO -- With the D-backs in the hunt for a return trip to the postseason, the rotation -- especially the 1-2 punch of Zac Gallen and Merrill Kelly -- is key to the team's aspirations of making another deep run.

Both Gallen and Kelly had faltered some after injured-list stints that ended in June and August, respectively. But the duo is showing signs of turning the corner.

One day after Gallen fired six hitless frames, Kelly put together one of his best outings of the season before the Giants walked off the D-backs, 3-2, on Thursday at Oracle Park. The veteran right-hander struck out eight against no walks across seven innings of two-run ball, but had to settle for a no-decision after departing in a tied ballgame.

"He had that presence. He had that type of day," manager Torey Lovullo said. "I know there were some moments where he could take some pitches back, but overall, it was seven quality innings, two runs. He was throwing any pitch at any time, had a lot of swing-and-miss, had some big outs at the right time."

The D-backs' bullpen, which was leaky in the first two games of the series, could not hold the line and send the game to extras with no margin for error. Patrick Bailey hit the walk-off winner off Kevin Ginkel, driving a ground-rule double to left-center to score Tyler Fitzgerald, who had singled to lead off the frame before stealing second to give the Giants a runner in scoring position with nobody out.

While Arizona fell short of the sweep, taking two of three from San Francisco was a rebound from the previous 2-5 homestand. The D-backs remain five games back of the Dodgers in the NL West and are half a game out of the top NL Wild Card spot after the Padres' 6-5 loss to the Tigers.

Regardless of Thursday's result, getting the top of the rotation back on the right track for the stretch run is invaluable.

"I think the offense has carried us the majority of the season," Gallen said Wednesday. "But I think when we're rolling and when we're really dangerous, the five guys in this rotation are leading us and the offense and the bullpen are putting teams away."

Kelly's strong start in San Francisco was a somewhat full-circle moment, as he had been slated to start against the Giants at Oracle Park in late April but was scratched with what was believed to be a minor injury. Kelly ended up missing nearly four months with a right shoulder strain, and he went 2-2 with a 6.75 ERA in his first four starts off the IL.

The pair of runs Kelly permitted in his strong return to the Giants' home ballpark also came by way of Bailey. After allowing his first two batters of the fourth inning to reach scoring position with nobody out, Kelly struck out two and was nearly out of the jam. But Bailey drove a 2-1 sinker into left field to put the Giants on the board.

After Kelly's afternoon was over, Lovullo pulled his starter aside for a long conversation, just like he had done with Gallen the night before. The discussion revolved around the at-bat against Bailey in the fourth -- Kelly had initially stepped off because he didn't want to go to his sinker in that spot, but he threw it anyway.

"I was basically just reiterating to him that that falls on me," Kelly said. "That's my responsibility, not only as the guy with the ball in my hand but also … a guy who's been around a lot longer [than rookie catcher Adrian Del Castillo]."

After his hitless outing the night before, Gallen mentioned that he had recently given Kelly some words of encouragement: "You don't have to expect too much out of yourself. Just get in a rhythm, get going."

The message resonated with Kelly, who knows that he's still capable of reaching his best form. It just comes with time.

"Zac's obviously seen me throw for six years now," Kelly said. "He knows what I look like when I'm going well; he knows what I look like when I'm going bad. And he probably also knows the faces that I wear. … Maybe he sensed that I was maybe pressing a little bit, and I think his message was spot on: Just keep going, trust the process and you're going to be all right."