Posey added an RBI double and a single as the Giants overcame a three-run deficit.
"Posey has been working on some things to get himself back on track or where he thinks he should be," Giants manager Bruce Bochy said. "It is important to get his timing and confidence, not that he didn't have confidence."
The Reds scored three quick runs off Tim Hudson.
Todd Frazier doubled home two runs in the first. Billy Hamilton doubled home Skip Schumaker, who started in left field, giving the Reds the lead after two innings.
Hunter Pence started his second game after resting a sore shoulder. He tripled after Posey's home run.
Ehire Adrianza hit his second home run of the spring, a two-run shot off Cingrani, who allowed six runs after pitching seven scoreless innings, including the first two innings of this appearance.
Adriana is relatively new to switch hitting.
"Adrianza has had a nice spring," Bochy said. "He's been balanced from both sides of the plate. He has been here awhile. He came in early to get ready for camp."
Schumaker, who signed a two-year deal with the Reds in November, doubled and hit a solo home run off Hudson. He is hitting .550 this spring.
Giants: Hudson allowed three runs in 4 1-3 innings on five hits and three walks. They were the first runs he allowed this spring. He is the second Giants starter to give up a run. Ryan Volgesong had allowed the only six runs against Giants starters in 31 innings until Todd Frazier doubled to drive in a pair Tuesday. Hudson pitched five scoreless innings coming into the game.
"I was able to get some good work in. It wasn't a walk in the park but it was what I needed. I got to run around the bases a little bit," Hudson said. "They laid off some pretty good pitches and they made me pay. I started making better pitches after I settled in."
The veteran pitcher had a double and single at the plate.
Reds: Cingrani, left-hander, had pitched five scoreless innings this spring, including three against the Giants and Hudson on Thursday. But the Giants chased him after 2 2-3 innings with eight hits. He allowed six runs on eight hits, five for extra bases.
"Cingrani is a guy working on a breaking ball and his and changeup," Cincinnati manager Bryan Price said. "You're not seeing the same pitching philosophy that you have in the past. We all agree he has to develop those pitches. There is not a better place to do it. You hate to lose a game when guys are working on their stuff but it will pay dividends down the road."
Giants: Outfielder Tyler Colvin has been held out of activity with discomfort in his back. He expects to be back in a couple days. ... Outfielders Michael Morse and Hunter Pence returned to action on Monday. Morse calf had healed. Pence is playing for the second straight day after pain in his shoulder subsided. ... First baseman Brandon Belt is out of action with an illness.
Reds: Jonathan Broxton is close to appearing in games. He threw live batting practice today. "He's done everything to give us confidence that he's ready," Price said. Broxton had surgery on his right forearm flexor in August. ... Sean Marshall is feeling better after having five days off to rest his left shoulder. Marshall had a problem with his shoulder last season, will resume a throwing program soon. "He had five bullpen sessions before we shut him down. He's feeling great now. We are just being super conservative now," Price said. ... Mat Latos threw his third bullpen session on Tuesday.
ONE MORE INNING
Reds closer Aroldis Chapman pitched three scoreless innings, allowing a hit and a walk with one strikeout. During the season he will not likely pitch more than two innings.
"We utilize the plan to get him stretched out so he can get connected to his changeup and slider," Price said. "It gives him more opportunity to get familiar with those pitches. Don't read anything into it. He's not going into the rotation."
PITCHERS SWING IT
As pitchers go deeper into games, they begin to get some at-bats. Hudson had two hits for the Giants in his two at-bats, extending a modest three-game hitting streak for Giants' starters.
Madison Bumgarner singled against the Giants' Future Stars on Sunday. Matt Cain singled against the Cubs on Monday.
"I was pretty much over matched on the first six pitches from Cingrani," said Hudson, a .170 hitter lifetime. "I was in a position that I knew a fastball was coming. I stuck my bat out there and he hit it. I'm at the point that I'm trying not get hurt when I'm up there."
DON'T ROCK THE CLUBHOUSE
The Reds have a diverse clubhouse and there is no single person that chooses the clubhouse music.
Sam LeCure grabbed the remote early in camp and was playing 60's and 70's rock such as Crosby, Stills and Nash's "Woodstock."
LeCure is the seventh child in his family and the next youngest is 10 years older.
He has taken some teasing about his choice of music.
"It's just a product of being in a baseball clubhouse," LeCure said. "You're going to get teased about a lot of things. Even if you have a good day."
First year manager Bryan Price, who held a meeting to set down guidelines for dress and hair styles, has no set rules on music.
"I don't mind music in the clubhouse. My concern is decibel level," Price said. "I don't like music screaming through the clubhouse. You never are going to find genre of music that is going to satisfy everyone in the clubhouse. If you have one guy in sole possession of all the music, no one wants that kind of environment."