For the Atlanta Braves, it was another night of missed chances.
Matt Carpenter's two-run double helped carry St. Louis past the slumping Braves, who shook up their lineup but still lost their seventh in a row, 4-3 on Monday.
The Cardinals scored three runs in the fifth inning, taking advantage of shaky defense by Atlanta's Gold Glove shortstop. In fact, Simmons had a couple of plays that could've been scored errors but were initially ruled hits. The second one was changed to an E-6 and turned out to be especially costly, leading to a pair of unearned runs.
St. Louis built a 4-0 lead and barely held on to win the series opener.
"It was big," Carpenter said. "Especially when we got out to a big lead, to be able to hold them off, that was big for us."
Pena had two hits, including a seventh-inning homer that brought the Braves within a run, but they couldn't overcome a 4-0 deficit.
Juston Upton took a called third strike from Trevor Rosenthal to end the game with the potential tying run at second base -- Upton's fourth strikeout of the night and extending Atlanta's woes with runners in scoring position.
The Braves were 1 for 12 in those situations and are 6 of 51 during their losing streak, though Freddie Freeman saw some encouraging signs.
"We hit some balls hard with runners on," he said. "We were in the game the whole game. We couldn't say that the past week."
The last time the Braves had such a lengthy skid was May 21-28, 2012, when they dropped eight in a row. Their longest losing streak last season was four straight.
Shelby Miller (4-2) got a shaky win, giving up six hits and two runs in five-plus innings. Trevor Rosenthal pitched out of trouble for his ninth save, giving up a leadoff single to Simmons. Jordan Schafer bunted the runner to second, but Pena flied out to right before Upton whiffed.
Harang (3-3) took the loss, though he pitched much better than his previous start, when he was pounded for nine runs by the Marlins. This time, he gave up four runs in six innings but only two were earned.
The game was scoreless until the fifth, when Peter Bourjos led off with a single before Mark Ellis grounded one off Simmons' glove. The shortstop, looking to make a force at second, appeared to take his eyes off the ball as it skipped past him.
After Miller bunted the runners to second and third, Carpenter doubled to right-center to bring them both in. Matt Holiday followed with a hard liner past third baseman Chris Johnson to make it 3-0.
"Those things happen," Harang said of Simmons' error. "I told him not to be too hard on himself. He's probably going to save my butt plenty of times this year."
St. Louis added another run in the fifth on Bourjos' RBI single, but Gonzalez challenged a call at third base that had seemingly given the Cardinals a 5-0 lead.
Yadier Molina's bases-loaded grounder ricocheted off Harang's leg, right to Johnson at third. He caught it and blindly stepped back in search of the bag and managed to barely nick it, as the replay showed. The called was quickly overturned after a review of only 37 seconds.
The Braves knocked out Miller in the bottom half of the sixth, the first three hitters reaching safely. The Cardinals went to the bullpen after Evan Gattis' RBI single, and B.J. Upton followed with a sacrifice fly off Pat Neshek.
Neshek escaped the jam by striking out Simmons.
The Cardinals sent pitcher RHP Joe Kelly back to St. Louis to continue his rehab from a strained left hamstring. "Joe just wasn't to the point where they thought they could push him, so keeping him around the rest of this road trip didn't make any sense," general manager John Mozeliak said. "I don't know I'd call it a setback as much as he just wasn't progressing as quickly as we wanted." ... Atlanta RHP Gavin Floyd will make his season debut when he starts Tuesday against LHP Tyler Lyons (0-2) of the Cardinals. Floyd is coming back from Tommy John surgery and will start in place of Ervin Santana, who has a bruised right thumb. ...