Soto drove the first pitch he saw from left-handed Padres starter Robbie Erlin into the seats in left-center to give the Nationals a 3-0 lead.

His homer, which ignited a five-run second inning for Washington, was one of four the Nationals hit off Erlin and reliever Bryan Mitchell.

Mark Reynolds hit solo home runs to lead off the third and seventh inning, respectively. Bryce Harper homered to lead off the fifth.

The win snapped both the Padres' three-game winning streak and the Nationals' three-game losing streak.

Soto struck out as a pinch hitter Sunday in his major league debut after being promoted from Double-A Harrisburg. Monday was the first time he started in left field. He finished the game 2-for-4 with the homer, three RBIs and two runs scored.

Reynolds opened the Nationals second with a single and moved to third on Pedro Severino's double ahead of Soto's homer. Wilmer Difo singled and scored on Trea Turner's two-out double. Harper then doubled home Turner for the 5-0 advantage. Reynolds' first homer gave the Nationals a 6-0 lead.

The Padres' only runs off Gio Gonzalez came on rookie Franmil Reyes' first major league homer -- an opposite-field drive to right in the fourth. Before both were called up, Reyes and Soto led the minor leagues with 14 homers each this season.

Soto is the youngest player in the majors since shortstop Jurickson Profar debuted with the Texas Rangers in 2012. Soto is regarded as the Nationals' second-best prospect and one of the top 15 prospects in baseball.

Gonzalez (5-2) held the Padres to two runs on two hits and three walks with five strikeouts over seven innings. Erlin (1-3) gave up six runs on seven hits (including two homers) with two strikeouts in four innings. Mitchell allowed four runs on seven hits (two homers) and two walks in three innings.

Reynolds was 3-for-5 for Washington. Michael A. Taylor, Turner, Harper, Soto and Difo all had two hits for the Nationals.

--Field Level Media