SAN DIEGO -- First baseman Wil Myers drove in three runs with home run, a sacrifice fly and a double and right-hander Andrew Cashner allowed one run and three hits in six innings to pick up his first win of the season on Friday night as the San Diego Padres defeated the St. Louis Cardinals 4-1 at Petco Park.

Myers was 3-for-3, including his fourth homer of the season.

Cashner (1-1) and three relievers held the Cardinals to six hits. Fernando Rodney picked up his third save for the Padres.

Struggling right-hander Adam Waiwright (0-3) suffered the loss for the Cardinals. He gave up three runs, seven hits and a walk in six innings.

The Cardinals wasted excellent opportunities in the fifth and seventh with the Padres leading 3-1.

Pinch-hitter Aledmys Diaz opened the seventh with a single off Padres reliever Ryan Buchter and raced to third on a double by shortstop Ruben Tejada. When the throw to the infield got away, Diaz tried to score and was thrown out by third baseman Adam Rosales, who recovered the throw.

Cashner worked his way out of a jam in the fifth. Kolton Wong opened with a single and moved to second when Cashner hit Tejada with a pitch.

After Wainwright advanced Wong and Tejada with a sacrifice bunt, Cashner struck out Matt Carpenter to freeze the runners at second and third and retired Stephen Piscotty on a routine grounder to Jemile Weeks at second.

Myers helped the Padres take a 2-0 lead with a solo homer in the first and a sacrifice fly in the third.

Wainwright entered the game with an 8.27 ERA and had struggled with his opening pitches to hitters in his first three starts. Hitters were batting .706 on the first pitch they saw from Wainwright when Myers launched a 418-foot drive to right center on the first pitch he saw from the St. Louis right-hander.

Cashner led off the San Diego third with a bunt single pushed up the first-base line. Cashner raced to third when center fielder Jon Jay slashed a single off the glove of St. Louis first baseman Matt Adams, the ricochet rolling past Wong into short right center.

Cashner scored on Myers' liner to the warning track in right.

St. Louis got on the board in the fourth when Randal Grichuk lined a 432-homer into the Cardinals' bullpen in left center.

The Padres got the run back in the bottom half. Jemile Weeks singled with two outs and scored from first on Rosales' double to right center.

The Padres stretched their lead to 4-1 in seventh against Cardinals reliever Seth Maness.

Pinch-hitter Jose Pirela opened the inning with a double but was out at third on a failed sacrifice bunt by Jay. Myers doubled to right center, with Jay scoring from first.

NOTES: The Padres are promoting RHP Cesar Vargas from Double-A San Antonio to start Saturday night's game against the Cardinals in the spot vacated when LHP Robbie Erlin was placed on the 15-day disabled list with a forearm strain. ... The Padres promoted OF-2B Jose Pirela from Triple-A El Paso and optioned RHP Leonel Campos to the Chihuahuas. Campos was with the Padres one day and allowed seven runs (five earned) in one-third of an inning. ... The Cardinals gave veteran INF Ruben Tejada his second start at short Friday night while giving rookie Aledmys Diaz a game off. ... INF Jedd Gyorko was at Petco Park for the first time Friday since the Padres traded him to the Cardinals last winter for CF Jon Jay.