Wil Myers' first home run of the season gave San Diego the lead late in the game.
Justin Upton's 2nd home run of the year was a blast to left in the 8th inning.
Odrisamer Despaigne started in place of the injured Ian Kennedy.
It was the first career grand slam for backup catcher Wil Nieves.
Since 1996, the Padres have signed Matt LaChappa to a rookie contract every single year.