SAN FRANCISCO -- Five days ago, the Giants came back from a four-run deficit to topple Reds right-hander and reigning National League Pitcher of the Month Luis Castillo at Great American Ball Park. They found themselves in a similar spot Friday night, but they couldn’t dig themselves out of an early hole against Castillo for a second time.

After scoring 49 runs over their six-game road trip to Cincinnati and Colorado, the Giants’ bats came crashing down to earth in a 7-0 loss to the Reds at Oracle Park. They mustered only two hits -- a single and a double by Stephen Vogt -- against Castillo, a former Giants farmhand who struck out 11 over six innings to lower his ERA to 1.76 on the season, the third-lowest mark in the Majors.

“The whole game, it seemed like we had a couple or a few chances there to maybe break it open, but he’s got a plus fastball and changeup,” manager Bruce Bochy said. “You have your work cut out when you’re going against him.”

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The Giants didn’t do themselves any favors after allowing the Reds to score four unearned runs off right-hander Dereck Rodríguez following a costly error from left fielder Tyler Austin in the second inning.

Making only his sixth start in the outfield this season, Austin allowed a routine fly ball from Derek Dietrich to clang off his glove and drop in left field. While Austin played outfield in the Minors, his big league experience there is limited, as he mostly played first base and designated hitter for the Twins before being traded to the Giants last month.

The Giants have been trying to get Austin more reps in left field before games, but the acclimation process has been slowed by a bout of elbow inflammation and inclement weather on the road.

“He just doesn’t have a lot of time out there,” Bochy said. “You get a guy swinging the bat the way he is, you try to find some time for him occasionally out there, but we’ll get some work out there with him and it’s going to get better. He’s played out there before, he just hasn’t been out there in a while.”

Jose Iglesias followed Austin’s miscue with a single to put runners on first and second, but Rodriguez nearly escaped the inning unscathed after appearing to induce a double play on a popped-up bunt attempt from Castillo. The Reds challenged the call, and Iglesias was declared safe at first base following a replay review, keeping the inning alive.

Rodriguez struggled to contain the damage after that, yielding an RBI single to Tucker Barnhart, a two-run triple to Nick Senzel that popped out of Steven Duggar’s glove after he crashed into the center-field wall and an RBI double to Eugenio Suarez.

“Those are things that happen in the game,” Rodriguez said. “It was my job to try to pick them up and try to get the big out and I wasn’t able to. It was a rough inning. I was just happy I was able to bounce back after that and put up some zeros.”

Rodriguez departed after five innings with the Giants trailing by four, though the outing still marked a step forward from his previous two starts, when he gave up a combined 14 runs (12 earned) over eight innings.

“I still feel like my command is a little bit off like I was saying the past two outings,” Rodriguez said. “But we’ll get there.”