Lopez is one of several young pitchers on the Chicago staff that has continued to mature in September, a month Renteria considers an evaluation period for the organization.
"It's experience. I think their ability to make sure that they deal with things that are important," Renteria said. "Sometimes you get caught up in little minutia and you make it more important than it is. I think the reality is, is if you focus on what you're supposed to be doing -- I know they are cliches -- you can control what you can control and do what you can with everything else."
Along with rookies Carson Fulmer, Dylan Covey and Lucas Giolito, Lopez spent time this season between Chicago and Triple-A Charlotte. While Lopez was discouraged to begin the season in the Minor Leagues, he understands why that decision was made and he now views that as a valuable experience.
"I think that experience I gained this year in Triple-A has helped me to be here as a better pitcher, a mature pitcher with a better understanding of the game," Lopez said. "This season is just to gain experience. We're trying to get the most experience we can for future seasons.
"We hope that next year we can do better and we can be competing. I think that's our goal, and that's the way we have to approach this process."
In their last eight combined starts, the young quartet of Lopez, Fulmer, Covey and Giolito have gone 3-3 with a 3.35 ERA. Lopez isn't alone in understanding Renteria's sentiments that this September is for improvement and evaluation.
"I think with the circumstances we have now, there's a lot of room to grow as a baseball player and learn," Fulmer said after Friday's start. "The veteran guys on the staff, we are around them on and off the field, and we're just trying to soak in as much as we can. If we worry about the small things and do everything we can, we'll continue to grow and have success as an organization and as a team."
On top of battling a head cold, Lopez's maturity and composure were on display when he was able to work past a 31-pitch fourth inning Saturday and retire nine of the last 12 batters he faced en route to a season-high seven-inning outing.
"It was a constant battle for me because it wasn't really good, but I think it was, under the circumstances, a very good outing," Lopez said. "I'm proud of myself because I was able to battle through that discomfort I was feeling."