The Giants’ longest road trip of the season ended in dispiriting fashion.

With two of their hottest hitters, Donovan Solano and Austin Slater, unavailable, the Giants went quietly in a 5-1 defeat to the Astros that secured their third consecutive series loss on Wednesday night at Minute Maid Park.

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The Giants (8-12) slipped four games under .500 with one-third of this 60-game season in the books. They went 3-7 on their 10-game road trip to Colorado, Los Angeles and Houston and will now attempt to reset with an off-day Thursday before kicking off a Bay Bridge series against the A’s on Friday.

“We have to play an all-around brand of baseball if we’re going to go on the road and play the Rockies, the Dodgers and -- I know they haven’t gotten off to their best start -- but a very talented and capable team in the Astros,” manager Gabe Kapler said. “We have to play really, really high-level all-around baseball. We just didn’t do that.”

The Giants jumped out to a 1-0 lead after Mike Yastrzemski tripled and scored on a single by Alex Dickerson in the first inning. But they were held scoreless for the rest of the night by Astros right-hander Zack Greinke, who departed after striking out seven over 6 1/3 innings.

San Francisco’s offense has consistently shown its resilience late in games this season, but it was missing two key bats on Wednesday. Solano, who leads the team with a .458 batting average and is riding a 15-game hitting streak, was out of the starting lineup for the second consecutive game with abdominal soreness. Slater was penciled in to hit third against Greinke after going 8-for-21 (.381) with three home runs over his last six games, but he was a late scratch with right elbow soreness.

Kapler said Slater first felt the elbow issue during Tuesday’s game, and it didn’t warm up the way he hoped it would on Wednesday. The 27-year-old outfielder will be reevaluated when the club returns to San Francisco.

The emergence of Yastrzemski, Solano and Slater has helped carry the Giants’ lineup in recent weeks, but Wednesday’s injuries exposed the struggles of the veterans who were expected to serve as the primary offensive pacesetters this year. Evan Longoria (.213 average), Brandon Crawford (.208), Brandon Belt (.135), Pablo Sandoval (.179) and Hunter Pence (.105) have been mired in deep ruts to start the season, though Pence showed signs of turning a corner after delivering a huge pinch-hit, three-run home run on Tuesday.

“I think it’s the responsibility of the team to come together and perform as a group,” Kapler said. “I don’t ever put the onus on any one individual, or even on two or three. I think the right way to look at this is when one guy is struggling or not consistent, then the rest of the group has to surround that player or that group of players with support.”

Trevor Cahill did not make it out of the second inning after exhausting his prescribed pitch count in his season debut with the Giants. Cahill, who started in place of the injured Jeff Samardzija, missed the first few weeks of the regular season after sustaining a fingernail injury while repairing his bike and wasn’t built up to throw more than 45 to 50 pitches.

Cahill did not allow a hit, but he walked four of the nine batters he faced and exited after loading the bases with two outs in the second. He needed 55 pitches to record five outs and was replaced by Shaun Anderson, who induced a popout from George Springer to end the inning.

“They had some good at-bats today,” Cahill said. “This was one of those games where you walk four guys but you didn’t feel super uncompetitive in any at-bat in particular. They just won some battles. I wasn’t about to give in. They took some good pitches and some calls didn’t go my way. I felt like I had a decent idea of where everything was going, which was good for me. I just think everything wasn’t as sharp as I wanted it to be.”

The Astros tied the game on Alex Bregman’s RBI single off Dereck Rodríguez in the fifth before pulling away with a four-run sixth. Rookie left-hander Caleb Baragar yielded four consecutive hits to open the inning, including a three-run shot to Martín Maldonado that extended Houston’s lead to 5-1.

“He’s targeting the top of the zone, but he’s missing down in the zone,” Kapler said of Baragar. “When you have a fastball that carries, you really want to execute up. Right now, he’s just kind of pulling the ball down. That’s just an easier pitch for hitters to handle, and they’re doing damage on it right now.”

The Giants have struggled to limit the long ball this season, as their 30 home runs allowed ranks second only to the D-backs (43) in 2020. San Francisco pitchers have yielded at least one home run in 16 consecutive games, the longest such streak in franchise history.