PITTSBURGH -- The Cardinals’ bullpen has been one of the most reliable in the Major Leagues in the second half. Entering action on Friday, they led all teams with a 3.27 ERA since the All-Star break to help produce a strong postseason push.

But against the Pirates on Friday, the bullpen fell apart in an inning’s time, sending St. Louis to a 9-4 loss at PNC Park. It snapped the Cardinals’ streak of eight consecutive wins in Pittsburgh, but they held their 2 1/2-game lead over the second-place Cubs in the National League Central, with Chicago falling to the Brewers.

• Box score

The seventh inning started with the Cardinals up, 4-1, but also with a leadoff single for Cole Tucker off John Gant, who exited after recording an out and walking Kevin Newman.

Andrew Miller struck out the hot-swinging Bryan Reynolds, but gave up three singles in succession, beginning with what was a bit of a misplay and a bit of the beast of baseball.

Miller put Starling Marte behind 0-1 with two outs, but left a fastball high and inside. Marte chopped it to shortstop Paul DeJong, and the ball bobbled a bit in DeJong’s glove as he tried to flip it to second baseman Kolten Wong for the forceout of Newman, but the relay was tardy.

“That’s what he’s kind of known for,” Cardinals manager Mike Shildt said of Marte's infield single. “The ball comes in, and we just couldn’t get the force at second, and we kind of went from there.”

Given Marte’s speed -- his 29.0 mph sprint speed, according to Statcast, is the best on the Pirates -- the play at first likely would have been tight.

“It’s hard to say,” Shildt said. “Marte got jammed a little bit, so I don’t know if he [had a] jailbreak out of the box. … It’s probably going to be a [bang-bang] either way at first or second.”

Regardless, the play set up the three hits off Miller, with the final one from Melky Cabrera allowing the Pirates to tie the game.

“Being behind 2-1 [to Cabrera], the way that inning’s going, I’m just trying to create action and left it up too middle,” Miller said. “And his hand-eye coordination, bat-to-ball is just so good that he’s going to do exactly what he did.”

John Brebbia entered to try for the final out in the frame, but gave up a single to Jose Osuna and a triple to Adam Frazier before getting Tucker to ground out, capping a six-run rally for the Pirates.

With Marte’s chopper to DeJong and Josh Bell’s popped-up single that evaded three defenders after that, the Pirates’ offense also bucked a trend for the Cardinals’ defense, a group -- like the bullpen -- which has been stellar recently. Their 12.8 Defensive Runs Above Average (Def), per FanGraphs, leads the Majors over the past 30 days.

“Far and away, they’ve been such a positive force,” Miller said. “Things happen, that’s baseball, that’s the way it goes. I think that, all around, our defense and our positioning and all that stuff is as good as it gets.”

But as is true of all trends in baseball, sooner or later, it’s bound to be broken, if just for an inning.

“It was one of those nights, you know,” Frazier said. “Some nights, you can’t get any of those; you feel like they get all of those. Tonight, we got a couple breaks.”