It was a first inning on Tuesday night that was more befitting of Great American Ball Park than Oracle Park. Never before had four home runs left the 21-year-old facility in the first inning.

Almost more surprising was that it happened on the watch of Reds starter Luis Castillo and the Giants' Kevin Gausman. They each traded a pair of long balls before the game was settled by the bullpens as Cincinnati ultimately dropped a 7-6 decision.

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Gausman, who had a brief 2019 tenure with the Reds, took a 1.32 ERA into the night through two starts. But on a blustery evening, the visitors pounced quickly. Joey Votto hit his second homer in as many days -- a two-run shot to left field. Mike Moustakas added his own two-run drive to right field and into McCovey Cove to make it a 4-0 lead.

Normally in the hands of Castillo, such a lead would be safe, but San Francisco erased it in a snap. His second batter, Mike Yastrzemski, lifted a 2-2 fastball for a two-run homer to right field.

"When that home run went out to right-center field I thought it was just a routine play by our guys. I saw that ball carry in the wind a little more and said, ‘OK it’s a home run now,’" Castillo said via translator Jorge Merlos. "Just had to deal with it."

With two outs, Brandon Crawford drove a 3-1 fastball to left field to make it a 4-4 game.

Television cameras caught Reds catcher Tucker Barnhart slam his glove on the bench in frustration when the inning finally ended.

"The first inning wasn’t the greatest," Castillo said. "Tucker and I weren’t on the same page in the first inning, but we talked in between innings and we got on the same page. He asked me for the pitches, I asked him for other pitches and we just got on the right page after that."

Last season, Castillo had a 5.33 ERA in five games while working with Barnhart, and a 2.01 ERA in seven starts with Curt Casali behind the plate. Casali was at Tuesday's game, but watching from the dugout as a member of the Giants.

Barnhart has caught all three of Castillo's starts in 2021. On April 1 vs. the Cardinals, the right-hander gave up 10 runs (eight earned) over 3 1/3 innings. But the two were very much in-sync on April 7 vs. the Pirates, when Castillo cruised for seven scoreless innings.

"Luis Castillo is an outstanding pitcher. Tucker Barnhart is a great defensive catcher," Reds manager David Bell said. "I have no concerns at all that that’s an issue, and we'll continue to do the work. I'm proud of the way our team, our catchers, our pitchers, how we prepare for every series, for every game. It’s a very comprehensive plan, so I feel good about that, and it’ll pay off."

Castillo settled in and retired 11 of the next 12 batters following the Crawford homer and worked with a 5-4 lead from the second inning. Following a pair of one-out singles in the fifth inning that put the tying run on third base, he escaped with an Alex Dickerson comebacker that he turned for a double play.

"Overall it was a good outing," said Castillo, who allowed four earned runs and seven hits with no walks and seven strikeouts. "We learned after that first inning what was going on and what was working for us and what wasn’t working for us. We could learn from that inning and take us through the rest of the outing. It was helpful for us, we were able to work on our pitches and work through the batters as we went along. And of course that double play really helped us in that inning as well."

When the Reds needed some zeros dealt by their relievers, they weren't there. In the bottom of the sixth, lefty Sean Doolittle surrendered an Evan Longoria solo homer to left field and a two-out single by Buster Posey. Pinch-hitter Austin Slater drove an RBI triple to right-center field off Carson Fulmer to put the Reds down by one run.

It was a 6-6 game when Reds lefty Cionel Pérez walked his first two batters in the bottom of the seventh inning to set up the go-ahead run. Lucas Sims took over with one out when Wilmer Flores lifted a sacrifice fly that scored Donovan Solano.

"It makes it tough when the first couple guys get on," Bell said.