Smith (5-6) allowed four hits and two walks, striking out five. He leads all National League rookies in strikeouts, and his punchout rate of 29.6 percent ranks 12th among all major league pitchers.

Rookie right fielder Brian Anderson led the Marlins offensively, going 3-for-5.

Padres rookie left-hander Eric Lauer (2-4) took the loss, allowing six hits, a career-high seven walks and three runs in five innings.

The Marlins used one of those walks to start a rally in the fourth. Justin Bour drew a base on balls, advanced to third on Cameron Maybin's double and scored the game's first run on Lewis Brinson's sacrifice fly, which reached the warning track in left.

Miami padded its lead to 2-0 later in the inning. With two outs, Lauer intentionally walked Yadiel Rivera to get to Smith, who lined a first-pitch fastball to right for an opposite-field single.

Lauer got in trouble again in the fifth, loading the bases with two outs on singles by Bour and Maybin and a walk to Brinson. Rivera then drew an RBI walk before Smith was retired on a groundout.

San Diego had an opportunity to get back in the game in the sixth, loading the bases with one out. Marlins manager Don Mattingly removed Smith in favor of Brad Ziegler, who induced an inning-ending double-play grounder by pinch hitter Cory Spangenberg.

Miami stretched its lead to 4-0 in the bottom of the sixth. Starlin Castro singled, raced to third on a single by Anderson and scored on a groundout by J.T. Realmuto, who used his speed to avoid a double play.

The Marlins' bullpen closed out the game as three relievers - Ziegler, Drew Steckenrider and Kyle Barraclough -- combined to pitch 3 2/3 scoreless innings, completing a six-hit shutout.

--Field Level Media