Padres third baseman Yangervis Solarte whacked a solo home run off Cardinals starter Carlos Martinez in the top of the fourth inning, giving San Diego a 1-0 lead.
Solarte's home run came on a 2-0 pitch and went 407 feet. It was his fourth home run of the season and the second against the Cardinals in this series.
Martinez retired the next three batters.
Cards-Padres scoreless through three innings
Through three innings of play, the Cardinals and Padres are scoreless on the Fourth of July.
Jhonny Peralta's first-inning single is the only hit by a Cardinal batter so far.