PITTSBURGH -- The St. Louis Cardinals have seven games remaining on this road trip, all against losing-record teams.

Uh oh.

Daniel McCutchen pitched six shutout innings for his third victory as a major league starter, Neil Walker tripled with the bases loaded and the Pittsburgh Pirates dealt the Cardinals another damaging loss by winning 5-2 on Wednesday night.

Dropping their fourth consecutive series against a losing-record team, the Cardinals fell 3 1/2 games behind Cincinnati in the NL Central. St. Louis also remained a game back in the NL wild card race.

The Pirates, on pace to lose more than 100 games, had lost 13 of 15 before beating St. Louis on successive nights. Walker, a rookie batting .325 since July 17, also drove in three runs as Pittsburgh won 4-3 on Tuesday.

"This is the quality of baseball we need to be playing on a daily basis," Walker said. "How we played these last couple of days is what we're striving for on a daily basis."

Jake Westbrook (1-2) got into trouble in the third by hitting Chris Snyder with a pitch and Andrew McCutchen beat out an infield single. Walker tripled to center on a 3-2 pitch.

"I didn't want to walk him," Westbrook said. "I put a sinker down in the zone and he did a good job. He put a good swing on it."

Jose Tabata, another rookie, made it 4-0 an inning later with an RBI single, his sixth hit of the three-game series.

The Cardinals have fallen into an unusual pattern since the All-Star break. They beat good teams but lose to mediocre or bad ones. They are 12-2 against top clubs but 9-13 against teams that are .500 or own losing records. They have dropped series to the Astros, Cubs, Brewers and Pirates this month alone.

"I don't care if it's home, the beginning of a road trip, the middle of a road trip, this is a disappointing series to lose," Cardinals manager Tony La Russa said. "Our goal is to win the series, and if you win the first game of a series, you're in charge."

McCutchen (2-5) wasn't scheduled to start, only to learn Tuesday night that scheduled starter Jeff Karstens was being skipped due to arm fatigue. The right-hander responded with the best of his 14 career starts, striking out five and walking two while giving up three hits.

"It was his day," Cardinals infielder Felipe Lopez said. "I don't want to talk bad about anybody, but I think we could have got him. We were just chasing bad pitches."

Before making the spot start, McCutchen had a 1.74 ERA in nine consecutive relief appearances. Pirates manager John Russell said he's returning to the bullpen.

"We were hoping to get four, five innings out of him," Russell said.