"As far as his delivery goes, he was more under control tonight than he has been all year," Harkey said of Marmol. "He's been doing a lot of work to fix his delivery. Continuing to stay within himself is going to be a big key."
Marmol fell one shy of tying his season-high 10 strikeouts. He had walked seven batters in his previous two outings entering the night.
"We've worked a lot on his direction lately and he needs to understand that that's going to be a big key to his success," said Harkey.
Marmol, who went 2-for-2 at the plate with a double, left the game in the eighth inning after being lifted for a pinch-hitter. He did not surrender a hit to the final 10 batters he faced, throwing 87 pitches – 61 for strikes.
Five of Marmol's strikeout victims were caught looking as the 24-year-old Cubs prospect relied heavily on his breaking ball in two-strike situations.
Both home runs that he allowed came after he fell behind in the count.
"My curveball was very good tonight and it worked, but I was able to get my fastball across for strikes, too," Marmol said after the game.
Iowa (15-15) reliever Randy Wells, who was responsible for charting Marmol's pitch speeds with the radar gun, said afterward that Marmol topped out at 96 mph in the game and was consistently in the low to mid 90s throughout the night.
"I felt I got back to basics tonight," Marmol said.
Angel Pagan had two hits in the game, including a towering solo home run to left field in the first inning that gave the Cubs a 1-0 lead.
Tony Richie picked up two hits in his first start behind the plate since being brought up from Double-A Tennessee on Friday. With the score tied 2-2, Richie brought home the game-winning run in the eighth inning on a bang-bang play at first base that allowed Scott Moore to score from third.