Pirates 6, Cardinals 4: Neil Walker homered and drove in four runs as Pittsburgh rallied against visiting St. Louis to win the opener of a three-game series.

Jordy Mercer went 3-for-4 and Walker also had three hits, including a three-run blast in the seventh inning off Carlos Martinez (0-2) that helped the Pirates win their third straight. Justin Wilson (1-0) struck out the only batter he faced in the seventh and Tony Watson pitched a scoreless eighth before Mark Melancon worked around a leadoff double in the ninth for his third save.

Cardinals starter Michael Wacha fell behind in the first inning after allowing back-to-back singles to Jose Tabata and Walker, both of whom scored with two outs on Ike Davis’ ground-rule double to left field. Wacha remained winless since April 13 while striking out seven and allowing three runs over five innings.

St. Louis pulled ahead in the fourth when Allen Craig snapped a 2-for-21 slump with a three-run homer off Francisco Liriano, who walked four and yielded three runs in five frames. Walker’s RBI single tied the game in the fifth before the Cardinals reclaimed the lead on Jhonny Peralta’s solo homer off Jeanmar Gomez with one out in the seventh.

Pittsburgh answered in the bottom half against Martinez, who allowed consecutive singles to Mercer and pinch-hitter Gaby Sanchez before Walker crushed his seventh homer over the right field wall. Peralta and Craig had two hits apiece for the Cardinals, who fell to 2-4 on their nine-game road trip.

GAME NOTEBOOK: The game was delayed by rain for 26 minutes in the top of the fourth inning. … Pirates OF Travis Snider and C Russell Martin lost their suspension appeals for their involvement in last month’s bench-clearing brawl with Milwaukee. Snider began his two-game suspension Friday, and Martin will sit out one game when he returns from the disabled list. … The Cardinals optioned OF Randal Grichuk to Triple-A Memphis and recalled OF Joey Butler.