The Pittsburgh Pirates took out a week's worth of frustration with one huge game on Tuesday night against the St. Louis Cardinals.

Nobody felt the brunt of it more than Cards catcher Yadier Molina.

The Pirates now go for a much-needed series victory on Wednesday in the finale of a three-game series with the Cardinals, who will likely be without their star backstopper.

Pittsburgh had dropped six of seven since a 19-inning win over St. Louis on Aug. 19, but after losing Monday's opener by one run it broke out with a 9-0 victory in the series' second game.

Pedro Alvarez paced the rout with four hits and a pair of homers, including a solo shot in the sixth inning that bounced out of the stands and headed towards the Allegheny River. The shot traveled an estimated 469 feet, the longest home run hit by a Pirates player at Pittsburgh's PNC Park.

"He can shrink a ballpark," Pirates manager Clint Hurdle said of Alvarez. "He has raw power."

Alvarez's power surge backed James McDonald, who picked up the win as he allowed just two hits and a walk with six strikeouts over seven scoreless innings.

Pittsburgh pulled to within two games of St. Louis for the NL's second wild card.

The Cardinals will have had plenty of time to watch the replay of Josh Harrison's high and violent collision at the plate in the second inning with Molina, one that left the All-Star catcher day-to-day with an upper back, left shoulder and neck strain.

Molina remarkably held on to the ball as Harrison was called out, but was unable to get to his feet for sometime before getting attended to.

"My back, my neck and my shoulder are a little sore," said Molina, who did not show signs of a concussion following tests during the game. "Hopefully with treatment I'll get better."

Jake Westbrook was touched for seven runs on 11 hits and four walks in five innings of the loss, St. Louis' second in eight games. It did fall seven games behind the Cincinnati Reds for first place in the NL Central.

Looking to pitch the Pirates to a series victory will be Wandy Rodriguez, who has yet to win as a starter since coming over in a deal with the Houston Astros prior to the non-waiver trade deadline.

Rodriguez did pick up his first win with Pittsburgh after throwing the final two innings of last Sunday's marathon win, but then dropped his seventh straight decision as a starter on Friday versus the Milwaukee Brewers. The left-hander yielded three runs on six hits and four walks over 6 2/3 innings.

After going 7-9 with a 3.9 earned run average in 21 games with the Astros this season, Rodriguez is 1-4 with a 4.86 ERA in six games with the Pirates.

The 33-year-old holds a lifetime record of 7-11 with a 3.73 ERA versus the Cardinals, who tonight replace Lance Lynn in the rotation with Joe Kelly.

The 24-year-old made his MLB debut on June 10, the first of 12 straight starts. The most recent was Aug. 14 and he then pitched twice in relief, including Friday at the Reds.

Kelly took over an ineffective Lynn after just two innings and got the win, allowing a run and striking out six over three innings. He improved to 4-5 with a 3.26 ERA on the season and hopes for a smooth transition back into the rotation.

"When I first started starting it didn't take much for me to get hot," said Kelly on the Cards' website. "I end up throwing more pitches to get a better routine, though, to become a starter. Whether you're doing bullpen or starting, you want to (have) damage control as much as you can and whenever you can."

The right-hander faced the Pirates for the first time in his career when he saw action in last Sunday's 19-inning loss. He hurled 5 2/3 innings and allowed one run.

The Pirates and Cardinals split 12 meetings this season prior to this series.