With the loss, the Cardinals now trail the Pirates by a game and a half and the Reds by 2 1/2.
"It's definitely not a team you can forget about and show up and just expect to beat," Cardinals starter Adam Wainwright said. "You have to go out and execute."
And that, at least from the fifth inning on, the Cardinals did not do well.
"We had a rough night tonight," manager Mike Matheny said. "They've been one of the best offensive teams here for the last month and we got an up-close look at that today."
Half of the Pirates' runs were scored off Wainwright, who had allowed only eight earned runs in his last four starts combined. After glowing about how in control he felt with his mechanics and pitch repertoire after his last outing, Wainwright watched the Pirates tee off on some poorly placed pitches, as well as capitalize on defensive shifts.
A two-out double by Neil Walker in the first put Pittsburgh ahead, 2-0. After the Cardinals moved in front, 5-2, Wainwright served up a two-out, bases-loaded double to Pedro Alvarez that evened the game in the fifth.
"That swing," Pirates manager Clint Hurdle acknowledged, "almost took the crowd out of it."
Wainwright, afterward, lamented not getting out of that inning unscathed. Two quick outs were followed by two routine grounders that would have been outs had the Cardinals' infielders been playing straight up. They became hits because a defensive shift was employed.
A walk followed, and then Alvarez's key hit.
"You live with it and you die with it," Wainwright said of the shift. "It's frustrating to give up two ground-ball hits to the infield like that."
Matheny opted to send Wainwright out to start the sixth, and things only further unraveled. Back-to-back homers by Clint Barmes and Alex Presley ended Wainwright's night. He allowed seven earned runs for the third time this season.
Though Wainwright has still won twice as many games as he's lost against Pittsburgh, his ERA in 19 games against the division opponent is a popping 5.20.
Wainwright wasn't the only Cardinals pitcher to feel the Pirates' wrath. The bullpen fared even worse.
Eduardo Sanchez allowed two runs on a Garrett Jones homer in the sixth. Fernando Salas loaded the bases with no outs in the eighth, and Sam Freeman allowed two of those inherited runners to score, including one on a bases-loaded walk.
Marc Rzepczynski served up a three-run homer to Andrew McCutchen -- his fourth hit of the night -- in the ninth.
"This year, there's no doubt, that when you think about our bullpen, it has hemorrhaged," Cardinals general manager John Mozeliak said on Friday. "Ultimately, this group has to become more consistent or we'll have to look for others who can become more consistent for us."
Indeed, the bullpen travails are hardly isolated. After posting a 2.70 ERA in April, the Cards' bullpen followed with a May ERA of 5.44. June has been only marginally better, at 5.26. That has left Matheny making every effort to successfully mix and match pitcher with situation.
Lately, the couplings have not produced desired results.
"We've got the parts," Matheny said. "Maybe [it's] just putting them together better, and that's my job. But I believe the talent that we have there is going to be enough to give us a chance to win."
In all, Pittsburgh tagged Cardinals pitching for a season-best 19 hits in the opener of this three-game series. A Pirates team that scored 147 runs in April and May combined has seemingly found a new identity. It has plated 139 runs in June.
"Obviously, they're ahead of us in the standings so they must be doing something right," first baseman Allen Craig said. "They have good young players. I'm definitely not surprised they came out and played well."
St. Louis spotted Wainwright those five early runs at the expense of Pittsburgh starter Kevin Correia. Craig doubled and scored in the second. An inning later, he launched a three-run homer.
He nearly drove home another in the fifth, but watched McCutchen track a fly ball to the center field wall to end the inning with a runner on the third. The game, at the time, was tied.
"He ran a long way to get that ball," said Craig, who has 37 RBIs in 37 games. "Against the wall, it's never easy to make a catch like that."
Carlos Beltran also had an RBI for a team-record seventh straight game, and it came on his 2,000th career hit. Beltran's seeing-eye single in the third scored Rafael Furcal and made Beltran the 29th switch-hitter in Major League history to reach that hit milestone.
"I was actually just trying to do my job and get the guy in and try to get on base," Beltran said, adding that he'll appreciate the achievement even more after some reflection.
The crowd acknowledged the career milestone with a standing ovation, to which Beltran doffed his helmet.