CINCINNATI -- It was a classic seventh-inning chess match on Thursday afternoon between San Diego Padres manager Andy Green and Cincinnati Reds manager Bryan Price.

Left-hander Brad Hand had not allowed a run since June 10. Scooter Gennett had hit .203 versus lefties this season. Price chose not to pinch-hit for Gennett. It was the best possible matchup for Green and the Padres.

Reds: Checkmate.

Gennett hit a grand slam on Hand's first pitch, and two pitches later, Eugenio Suarez added a solo shot, as Cincinnati rallied for a 10-3 victory over the Padres in the finale of a four-game series at Great American Ball Park.

"I think it was just a first-pitch slider for a strike," said Gennett. "(Price) is the type of manager that if you're starting, he's going to roll with what he's got. It's great to play for a manager like that."

With the Padres leading 3-2 with two Reds runners on and a 2-2 count on Joey Votto, Green replaced Kirby Yates with Hand, who had starting warming up when Votto came up to bat.

Hand walked Votto after two pitches to load the bases, then fanned Adam Duvall for the second out.

"We've got the lefty-lefty matchup that we honestly covet, that we would have gone to no matter what, Brad vs Scooter Gennett," said Green. "Brad's been great all year. He hung a breaking ball and he paid for it."

Gennett crushed the first pitch into the center-field seats for his third career grand slam, snapping Hand's career-high 24-inning scoreless streak.

"I had a pretty good idea it was gone," Gennett said.

On the next pitch after Gennett took a curtain call, Suarez launched a solo shot an estimated 451 feet to center putting Cincinnati ahead 7-3.

"It was just middle up, bases-loaded, trying to get ahead," Hand said. "I left a pitch up to Scooter and that was basically the end of it. I was warm. I can get hot very quick. As a matter of fact, I don't need many down there. My arm's loose."

It was the 20th home run of the season for both Gennett and Suarez.

Yates (2-3) was charged with two earned runs in one-third of an inning to take the loss. Drew Storen (3-2) pitched one-third of an inning and got the win.

Zack Cozart added a two-run home run and Votto a solo shot off Phil Maton in the eighth. It was Cozart's 14th of the season and Votto's 31st, extending Votto's hitting streak to 15 games.

Cincinnati (48-67) took three of four in the series but hasn't won a season series from the Padres since 2012. The Reds were swept in a three-game series at Petco Park in June and finished 3-4 against them this season.

Dinelson Lamet started for the Padres (50-64) and allowed two runs on three hits through five innings. He was in line to become the first San Diego hurler to win four consecutive starts since Jesse Hahn in 2014 before the bullpen imploded.

Reds rookie right-hander Luis Castillo made his 10th career start, allowing three earned runs on six hits in six-plus innings.

Tucker Barnhart doubled down the right-field line to drive in two runs in the second, putting the Reds ahead 2-0.

Wil Myers had the only two Padres' hits off Castillo through four innings. His 23rd home run of the season to center field in the fourth cut San Diego's deficit to 2-1. Myers homered to right field Wednesday night, snapping an 0-for-11 skid.

Second time through the order, the Padres got some better swings at Castillo.

Luis Torrens singled leading off the fifth and scored on Cory Spangenberg's double. Jose Pirela, who walked in his prior two at-bats, laced an RBI single to right, to put San Diego in front 3-2. It was Pirela's 12th hit in 25 at-bats versus Cincinnati this season. But the Padres bullpen couldn't maintain the lead.

"I like the guys to be in those situations," said Price. "I don't usually pinch-hit for our regular guys. Scooter's been a clutch guy for us. I thought if he made a mistake, he could get him. He did."

NOTES: Reds 1B Joey Votto's 15-game hitting streak is a team season-high and the longest active streak in the majors. ... The Reds reinstated from the paternity list C Devin Mesoraco and placed on the 10-day disabled list, retroactive to Monday, RHP Lisalverto Bonilla with right elbow inflammation. Mesoraco walked as a pinch hitter in the eighth. ... Yangervis Solarte started at SS for the Padres for only the third time this season and went 1-for-4. ... Reds RF Jesse Winker batted leadoff for the first time and went 0-for-3 with a walk. He made 10 appearances in the leadoff spot at Triple-A Louisville, batting .351.