The National League leader in RBI met a pitcher that had not allowed a run in 23 appearances with the bases loaded in a 1-0 game.
The matchup between Hoover and Goldschmidt has played out in the minor leagues over early years of each player's career.
Hoover was working on a string of 26-1/3 innings of shutout baseball over 23 appearances before an elevated fastball to the Diamondback's firstbaseman resulted in his third grand slam of the season and extended his league-leading RBI total to an even 100.
The game started as a matchup between two of the best young pitchers in the game. Tony Cingrani has excelled in place of the injured Johnny Cueto for the Reds.
Patrick Corbin started the season 9-0 for Arizona. In his 25 starts, Corbin has allowed two or fewer runs in 19 of them.
Both pitchers threw blanks at the opposition until the fourth inning.
Cingrani retired the first 10 Arizona batters. Corbin got the first six Reds until Devin Mesoraco led off the third with a double. Mesoraco advanced to third with two outs but Shin-Soo Choo grounded out to Goldschmidt.
Martin Prado hit his 12th home run of the season in the fourth.
Cingrani left the game with a strained lower back.
"I've felt it before," Cingrani said. "It came on gradually. I wanted to pitch through it but they didn't want me to."
"Cingrani was throwing the ball as well as he has all year," Dusty Baker said. "We didn't want to go to the bullpen that early. He said it's been bothering him for a couple weeks but he didn't say anything. Young pitchers don't want to come out of the rotation.
The Reds did little with Corbin, who notched his second complete game. Corbin started the eighth inning with a single that set up Goldschmidt's home run.
The Reds tried to get two innings from Sam LeCure but Corbin singled on an 0-2 pitch with one out. A.J. Pollack singled to right.
"The Diamondbacks have a couple hot hitters, Prado and Goldschmidt," Baker said. "We didn't want to bring in Hoover in that situation. We were trying to get a double play out of Prado. He has hit into 21 of them."
They got a ground ball from Prado but it found the hole between first and second. The single loaded te bases.
Hoover was brought to the mound to face Goldschmidt.
"I left a ball up to him," Hoover said. "I faced him a lot in the minors and you can't leave a fastball up to him on a 3-2 pitch. I'm just going to go back to what I've been doing, attack with my fastball."
Chris Heisey, who was brought in on a double switch with Hoover, hit his seventh home run with Zack Cozart on base to spoil Corbin's shutout.