SAN FRANCISCO -- This wasn't the start Luke Weaver imagined he'd have when he woke up Tuesday morning. It wasn't even the start the D-backs right-hander thought he had going when he punched out the first two hitters.

But given the way the rest of the first inning transpired, it was a start Weaver ended on a positive note, despite the D-backs taking their 107th loss of the season by a 6-4 margin to the Giants in the series opener at Oracle Park.

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In what may have been his final start of 2021, Weaver came out firing fastballs aggressively for his first two strikeouts. He thought he had fanned Buster Posey, too, on a close pitch, but Posey turned around and doubled.

Then, Weaver seemed to lose the feel for the strike zone, walking the next three hitters to force in a run, before striking out Evan Longoria looking to end the inning and leave the bases loaded.

Weaver was worn out by that point, having thrown a whopping 40 pitches to get the game's first three outs.

"That was one heck of a first inning," Weaver said. "And I don't think I've ever done that before, especially the walks. It's exhausting. I mean, those innings are tough, because when the pitch count starts to go up, the body energy starts to go down a little bit and you're competing over and over and over again. And you end up getting to 40 and you're running on fumes.

"So you're just still trying to execute pitches, so you kind of have this perfect storm going. And it just becomes a mental test. I obviously gave up the one run there, but I was just telling myself out there to still limit the damage and there's still a lot of game left. And that's just the message I took on the rest of the game."

That seemed to work, as Weaver made the best of the rest of his outing, holding the Giants scoreless each of the next three innings.

Each time Weaver came off the mound, he told pitching coach Matt Herges that he was going to get through five innings, but the Giants made Weaver work hard to get out of the fourth. And after the long first inning, Arizona manager Torey Lovullo was not going to push Weaver past the 93 pitches he ended up throwing.

"You're very concerned with that high pitch count in the first inning," Lovullo said. "So we decided to clip about 10 pitches off his overall number."

If this was Weaver's final start of 2021, he said he feels he can carry some momentum into next year, given the fact he feels he's ironed out some mechanical issues over the course of the season, as well as finally settled on a pitch mix.

While Weaver's fastball and changeup have always been there for him, developing a reliable third pitch has been a challenge. Maybe now, though, some combination of a cutter and curveball can fill that void.

"I feel great," Weaver said. "I feel like I can consistently throw at a higher velocity with probably a few adjustments and just really trying to hone in what I worked on this entire time. I think the command will be sharper. And consistently more cutters and some curveballs, like we saw tonight, will be reestablished. So there should be two pitches to depend on, but two other pitches to complement and to work in at the right times to make for a really good year."