CINCINNATI -- Tyler Stephenson had little time to think. The Reds’ rookie catcher was told he was pinch-hitting in the bottom of the seventh by bench coach Freddie Benavides if Jose Garcia could extend the inning.

Garcia battled reliever Sam Howard for a six-pitch at-bat after an 0-2 count and hit a two-out soft single into left field.

“[Bendavides] told me right beforehand, and the next thing you know, the next pitch, [Garcia] gets the single. So I’m still kind of getting my gloves on when I’m walking up,” Stephenson said.

Stephenson hit the second pitch he saw from Howard for a two-run home run to left-center field that gave the Reds a 3-1 victory over the Pirates in Game 1 of a doubleheader at Great American Ball Park on Monday.

• Box score

“First pitch, it’s a cutter-slider first pitch. He threw one down, good pitch, it was a ball,” Stephenson said. “And then the next pitch was elevated, and sure enough, that’s the one you want to hit, and I didn’t miss it.

“That’s what’s nice being here, we have the luxury of having cages down in the tunnel. I was hitting all game, just ready for an opportunity. I was loose and ready to go.”

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The most relieved person in the building was Reds starting pitcher Trevor Bauer, who saw his one-hit shutout bid evaporate in the top of the seventh inning when Colin Moran led off and lifted a 1-1 pitch into the first row of seats in right field for the game-tying home run.

Bauer struck out 12 batters over 6 1/3 innings with one earned run, four hits and two walks allowed. He was with pitching coach Derek Johnson when Stephenson left the dugout to go hit.

“I was standing next to DJ going over, just hating my life for giving up that homer,” Bauer said. “I'm just like, overanalyzing everything about it. Then we get a single and on his way up the stairs to take that at-bat, DJ's like, 'C'mon kid, let it rip.' He was all enthused about it.”

Pirates starter Cody Ponce held Cincinnati hitless for 3 2/3 innings and had faced the minimum number of batters. With two outs in the bottom of the fourth, Joey Votto launched a first-pitch sinker from Ponce into the left-center-field seats for his eighth homer of the season to break the scoreless tie.

“Getting the lead was huge,” Bauer said of Votto’s homer. “We got a lead and I was like, ‘I'm going to make this stand up, I've got a chance. I've got my chance now.’ I took it upon myself to make it stand up.”

Bauer enjoyed a run where he struck out seven of nine batters and had 11 K’s through six innings. When he ended the bottom of the sixth inning by getting Pirates rookie Ke’Bryan Hayes to look at a 96 mph fastball for strike three, the Reds’ starting pitcher let out a big yell. Out in center field, his teammates in the bullpen yelled with him in jubilation.

The no-decision did nothing to diminish Bauer’s chances for the National League Cy Young Award. His 1.71 ERA is second-best in the NL and he leads the league with 83 strikeouts and a 0.81 WHIP.

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Once Bauer lost his lead, he gave up a one-out single and two-out single. Manager David Bell emerged and went to Raisel Iglesias from the bullpen. Iglesias recorded back-to-back strikeouts to escape Bauer’s jam and set up the winning moment in the bottom half of the inning.

“Trevor was being Trevor, dominating all game. And then, sure enough, just one pitch ended up being a home run,” Stephenson said. “I mean, dude’s been pitching great all year. Then Iglesias comes in and it was good to come back and get a win.”

Stephenson, who is ranked as Cincinnati’s No. 4 prospect by MLB Pipeline, has assembled a nice resume after only five games over two stints in the big leagues:

• During his debut on July 27 vs. the Cubs, Stephenson hit a home run in his very first at-bat, one of three Reds to ever achieve the feat.

• Recalled last Tuesday, Stephenson started behind the plate on Thursday -- also vs. the Cubs. He threw out former Red Billy Hamilton trying to steal second base with a spectacularly perfect strike.

• And now, Stephenson already has a critical walk-off homer as his club is fighting for its postseason life.

“I can’t imagine everything that’s happened, really,” Stephenson said.