CINCINNATI -- Colin Moran has not been a very demonstrative player since he joined the Reds in March. But a long look at his sixth-inning drive to right-center field with a bat flip was all that was needed to know Moran really enjoyed his first big moment for Cincinnati -- a game-winning grand slam -- during Sunday's 7-3 victory over the Pirates at Great American Ball Park.

That also meant the 5-23 Reds earned their first series win of the season by taking two of three games from Pittsburgh.?

"The clubhouse is so happy for him. Just such a professional," Reds manager David Bell said. "He¡¯s handled everything so well. He started the season not playing a lot and he¡¯s just stayed ready. He¡¯s worked super hard, quiet. We know he can hit, so [to] do it right there against his old team, it was a great day."

Cincinnati trailed 2-0 and managed only two hits through five innings vs. Pirates starter Zach Thompson. Things turned in the bottom of the sixth against Pittsburgh lefty reliever Dillon Peters. Following a blooped single by Brandon Drury, Peters walked three straight batters, including Tommy Pham on four pitches, to force home a run.

For Peters, it ended the Major League's longest active scoreless streak at 16 2/3 innings.

With one out against right-handed reliever Heath Hembree, Moran lifted a 2-1 fastball over the middle of the plate to right-center field for the grand slam and his first homer of the season. The exit velocity, according to Statcast, was 108 mph, and the ball traveled 400 feet.

¡°I had been missing a lot of pitches, fouling a lot of pitches off, so it just felt good to finally feel the barrel," Moran said. "Obviously, a nice situation. It felt good to just come through for the team.¡±

Ahead of the plate appearance, teammate Albert Almora Jr. watched video with Moran and noticed a flaw with his swing.

"Almora helped me out. ¡­ Just that I was kind of pulling off the ball," Moran said. "Something simple. I appreciate stuff like that."

During the first inning of Saturday's 8-5 Reds loss to the Pirates in Game 2 of a doubleheader, Moran was robbed of a would-be homer that was caught above the wall by right fielder Jack Suwinski.

On Sunday, Suwinski could only watch as Moran's drive landed several rows of seats beyond the fence.

¡°I felt like I was getting closer," Moran said. "I feel like I am taking better at-bats and stuff like that. Yesterday, I felt like I was just missing balls. It was frustrating, so it felt good to hit the barrel that much better today rather than just off the barrel.¡±

Pittsburgh narrowed the Reds' lead to 5-3 after Bryan Reynolds hit a solo homer against Dauri Moreta with two outs in the top of the eighth inning. In the bottom of the eighth with one out, Moran lifted a 2-0 fastball from Chase De Jong for a two-run homer to center field.

That gave Moran a career-high six RBIs, and it was the third multi-homer game of his career. Of the 47 homers he's hit for his career, nine of them have come at GABP. Eight of them came as a member of the Pirates, when Bell often viewed Moran as a nemesis vs. the Reds.

"We know Colin well. We knew coming into the season he can hit. Great approach at the plate," Bell said. "He definitely hurt us a lot on the other side. We¡¯re happy to have him on our team. He¡¯s continued to do the same thing for us in a little bit more challenging role, really, just trying to stay ready."

A corner infielder, the lefty-hitting Moran played sparingly throughout much of the first month of the season. Since Joey Votto went on the COVID-19 IL on Tuesday, Moran has been at first base.

¡°Any time you can get regular at-bats, it helps," he said. "Just try to have a good at-bat, no matter what the situation you¡¯re put in. That¡¯s my role. I know we have a lot of talented players. I was just trying to do my part to help us win ballgames.¡±

During a frustrating first month of games, the Reds' clubhouse had often been subdued after so many losses. A series win was a much-welcomed boost.

"Any time we can get a win, we're going to enjoy it," said reliever Art Warren, who earned the win with scoreless sixth and seventh innings of work. "We're going to celebrate it and build off it for our next series and next game. Spirits are high right now, and we're happy for a win."