San Diego took the final two games in the three-game series.

The Padres trailed 2-0 going into the bottom of the fifth, and Reds starter Luis Castillo was working on a two-hit shutout.

Rookie Franmil Reyes and Freddy Galvis opened the bottom of the fifth with singles, and Manuel Margot drew a full-count walk to load the bases. Reyes was forced at home when Raffy Lopez topped a ball in front of the plate that Castillo fielded.

That brought up Renfroe as the pinch hitter for Padres starter Tyson Ross. Castillo threw two quick strikes before throwing a ball. Renfroe then launched the fourth pitch 375 feet off the second balcony of the Western Metal Supply Co. building down the left field line.

It was San Diego's first grand slam of the season, the third of Renfroe's career and the 12th pinch-hit grand slam in Padres history.

The Reds took a 1-0 lead in the second on Eugenio Suarez's 11th homer of the season on a 2-0 pitch from Ross. Cincinnati expanded the lead to 2-0 in the top of the fifth on singles by Jesse Winker, Joey Votto and Scooter Gennett.

Ross (5-3) allowed two runs on seven hits and two walks with three strikeouts. The Padres are 9-3 in games he has started this year. Kirby Yates picked up his first save of the season, getting Votto to ground out to end the game with two on.

A two-out RBI single by Lopez scored Reyes in the sixth to up the Padres' lead to 5-2.

The Padres used left-handed closer Brad Hand in the eighth to deal with left-handed hitters Votto and Scooter Gennett. Votto struck out, but Gennett homered for the second time in as many seasons off Hand to cut San Diego's lead to 5-3.

Cory Spangenberg greeted Reds reliever Raisel Iglesias with his fourth homer leading off the bottom of the eighth to make it 6-3.

--Field Level Media