SAN FRANCISCO -- Giants president of baseball operations Farhan Zaidi had two major items on his wish list heading into Friday’s Trade Deadline: a versatile bat and pitching depth.

He checked the first box by swinging a buzzer-beater deal for Cubs infielder/outfielder Kris Bryant. He checked the second with a smaller trade, reacquiring veteran reliever Tony Watson from the Angels.

Zaidi also explored the market for rotation help, but he ultimately couldn’t find a deal that made sense for the Giants, who were hesitant to part with the type of prospect capital required to land frontline starters like Max Scherzer and José Berríos.

With no supplementary pieces, the Giants will be relying on their current stable of starters to remain healthy and effective down the stretch. Still, there’s some cause for concern. Kevin Gausman has established himself as the ace of the pitching staff this year, but he’s looked increasingly mortal in the second half, a troubling trend that continued in the Giants’ 9-6 series-opening loss to the Astros on Friday night at Oracle Park.

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Gausman couldn’t get past the fifth inning for the third consecutive start, allowing three runs on six hits over 4 1/3 innings. Gausman struck out nine and walked two in the 83-pitch outing, but he’s still working to regain his feel for his signature splitter, which induced only two whiffs on Friday.

“That’s kind of been the issue the last couple of starts,” Gausman said. “I’ve just been really inconsistent with it. Missing off the plate when I’m trying to throw a strike, and missing on the plate when I’m trying to throw it off the plate. It’s been a little frustrating right now, but it’s a pitch that the more I throw, the more I find it, so I’ve just got to stick with it. It’ll definitely be there when I need it.”

Gausman’s night began on an inauspicious note, as the Astros forced him to throw 43 pitches in an arduous first inning. He managed to limit the damage to two runs and then appeared to right the ship by retiring 11 of the next 12 batters he faced, but he ran into trouble again in the fifth.

Jose Altuve led off the inning by belting a neck-high changeup out to left field to give the Astros a 3-2 lead. Gausman’s offering was 3.73 feet off the ground, making it the highest pitch that Altuve has homered on since Statcast began tracking in 2015. Gausman gave up a single to Michael Brantley and then struck out Yuli Gurriel before being replaced by lefty José Álvarez.

Altuve later broke the game open with his second home run of the night, brushing off “You’re a cheater” chants to deliver a grand slam off Jay Jackson and push Houston’s lead to 7-2 in the sixth. The Giants got a couple of runs back with the help of an error by Astros center fielder Kyle Tucker, who dropped a routine fly ball in the seventh, but their comeback bid ultimately came up short.

After finishing the first half with a sparkling 1.73 ERA -- the second-lowest mark in the Majors, behind Mets ace Jacob deGrom -- Gausman has now allowed 11 runs over 11 2/3 innings (8.49 ERA) over his last three starts, bumping his ERA to 2.35 on the season. Manager Gabe Kapler has said he believes the layoff over the All-Star break and family concerns -- Gausman’s wife, Taylor, was hospitalized due to complications with her pregnancy earlier this month -- have played a role in taking the 30-year-old right-hander out of sync.

Still, Kapler said he viewed Friday’s outing as a step in the right direction for Gausman.

“Obviously, it wasn’t an outcome that Gaus or any of us are thrilled about,” Kapler said. “We know that he’s capable of going deep into games and being a dominant starting pitcher in this league against the best lineups. I do feel like he was able to stay back a little bit better, which is one of the mechanical adjustments he’s looking to make. I thought the fastball had a little bit more life and a little bit more carry. I think the split is still a work in progress for him.”

Despite Gausman’s recent skid, the Giants’ starting rotation entered Friday with a 3.31 ERA, tied with the Mets for the third-best mark in the Majors. That success ultimately convinced Zaidi to stick with his current starting staff, which also includes Anthony DeSclafani, Alex Wood, Johnny Cueto and Logan Webb, but the Giants won’t have a ton of coverage in the event of injuries or regression in the second half.

“When you look at our rotation right now, we’ve got five guys who are throwing the ball really well,” Zaidi said. “If we did, you start thinking about, what are the implications for the roster? If you go out and get a starting pitcher, do you go to a six-man rotation? Does somebody go to the bullpen? Does it mean you have to move somebody else? We didn’t really like any of those options. Like we’ve talked about a lot in the last couple weeks, you kind of want to stick to the guys who got you here to a certain degree. Our starting rotation has certainly been that.”

The Giants will have to hope it stays that way.