Russell Martin doubled with the bases loaded and one out in the eighth and Travis Snider hit a leadoff homer in the ninth for the Pirates, who are still alive in the National League Central race while continuing to hold a Wild Card spot.
Doubront, acquired July 30 from the Red Sox, picked up his second win in his third start with the Cubs, and first ever at PNC Park. He credited pitching coach Chris Bosio with some key tips and feeling healthy for the turnaround.
"Everything went well today," Doubront said. "I was able to make good pitches to get quick outs and I'm really happy for that."
The Cubs struggled offensively during the seven-game skid, which coincided with All-Stars Starlin Castro and Anthony Rizzo sidelined with injuries. The six runs were the most scored since Chicago's last win, a 6-2 decision Sept. 3 over the Brewers.
Baez picked up the slack. Arismendy Alcantara singled to lead off the third against Jeff Locke, and Baez followed with his ninth home run to go ahead, 2-0.
"Apparently that's all he does," Locke said of Baez. "He's hitting below .200, he's finding the barrel that's for sure, and we've seen him strike out a ton. I left a changeup up, and he had that big swing on it."
Baez also was called out on strikes twice on some close calls.
"He had some really good at-bats today," Renteria said. "He was very patient in his at-bats and with some tough calls there. He showed extreme poise."
Welington Castillo hit a sacrifice fly and Mike Olt added an RBI double in the Chicago seventh, and Szczur connected in the eighth off Justin Wilson.
The Cubs need two more wins to top last year's record of 66-96 and have 14 games remaining. It's baby steps, but it'd be another plus for Renteria as he wraps up his first year on the job.
"Everybody has a sense of what the organization is trying to do, so maybe that's made it easier for me in my transition to manager as opposed to being a coach," Renteria said.
There have been plenty of challenges, and Renteria admitted to doing some things that might seem a little odd, such as batting Baez second or carrying an extra pitcher in the bullpen the majority of the season to protect the young arms.
Last week, Cubs president of baseball operations Theo Epstein was asked about Renteria's performance, and he complimented the first-year skipper on providing an environment for the young players to develop and thrive at the big league level. Cubs fans are getting a peek at the future with the promotions of players such as Baez, Alcantara, Kyle Hendricks and Jorge Soler. While player development was stressed this year, Renteria knows the emphasis could change.
"I don't worry about my job, never have," Renteria said. "I've never done that as a Minor League coach, big league coach. I focus on my job. I think there are a lot of good things in place here. I think the organization is moving in the right direction here. I sincerely believe that; I sincerely believed that when I first interviewed for this job. It's legitimate."