The win also halted a six-game losing streak for the Cardinals at PNC Park.

The teams, who meet again next weekend for four games in St. Louis, will decide this series Sunday after splitting the first two games.

Flaherty (2-1) allowed one run and four hits, with four strikeouts and two walks. He has picked up his first two major league wins in his past two starts as he helps fill the void with starter Adam Wainwright (elbow) out.

Bud Norris pitched a perfect ninth to improve to 10-for-10 in save opportunities.

Pirates starter Trevor Williams (5-3) lasted just four innings, giving up four runs and seven hits, with three strikeouts and no walks. He is 2-3 with three no-decisions after winning his first three starts.

The teams traded solo homers in the first.

Matt Carpenter led off the game with a shot to right, his fifth homer, for a 1-0 St. Louis lead.

Starling Marte, fresh off the disabled list (right oblique strain), clobbered a two-out pitch 447 feet over both bullpens in center to tie it.

The Cardinals took a 2-1 lead in the third. Yairo Munoz led off with a base hit, Flaherty sacrificed him to second and Jose Martinez drove him in with a two-out single.

In the fourth, Tommy Pham opened with a double down the line in left. Marcell Ozuna's single put runners at the corners. After Jedd Gyorko popped out in foul territory, Williams hit Dexter Fowler to load the bases.

St. Louis reported that Fowler, who writhed in pain after being hit on the right knee and left the game, had X-rays and was deemed day-to-day. Harrison Bader pinch-ran in his place.

Pham scored on Francisco Pena's fly ball to make it 3-1, and Munoz singled in Ozuna for a 4-1 St. Louis advantage.

--Field Level Media