For Miller, it was his second shortest start as a big leaguer. When the left-hander was with the Tigers, he lasted two-thirds of an inning on Aug. 29, 2007.
"The worst part of this game is we had to use the bullpen, which was already overworked," Marlins manager Edwin Rodriguez said.
All week, the bullpen had been heavily used. Last Wednesday, the team used all relievers against the Phillies because Josh Johnson was declared out due to a mid-back strain and right shoulder inflammation.
"Now that is going to kind of affect us pretty much the whole week," Rodriguez said of having a drained bullpen. "We have to regroup and see if one of the starters can give us six or seven innings so we can get that bullpen a well-deserved rest."
In all, seven Marlins pitchers combined to walk 12, which matches a team record in a nine-inning game. Previously, Florida walked 12 on Oct. 5, 2001 against Atlanta.
Miller has dropped three straight decisions, including back-to-back performances against the Phillies, in which he gave up 12 earned runs in nine innings.
Miller said it wasn't so much his mechanics on Sunday, and it had more to do with him being off.
"The last couple of ones against Philly, I felt pretty good," Miller said. "I made a few mistakes. I didn't feel that well at all today. I felt I didn't have command of anything. My stuff was bad. It was just all-around bad."
Chicago completed a three-game sweep behind Jeff Samardzija's solid six-inning performance. He allowed three runs on three hits while walking three and striking out four.
The Marlins have now lost a season-high six straight games, and they are mathematically eliminated from the National League East race.
Welington Castillo hit a two-run homer, his first Major League blast, and had three RBIs for Chicago.
Dan Uggla belted a two-run homer, while Hector Luna added his first career pinch-hit home run for Florida.
Logan Morrison, batting third for the first time all year, walked in the first inning to extend his string of reaching base safely to 38 straight games. Morrison now is third all-time in franchise history. Luis Castillo had a similar string of 46 games in 2002, and in the same year, Kevin Millar did it in 43 in a row.
The game featured a scary moment in Chicago's six-run second inning.
Rookie Tyler Colvin, after rounding third base on his way to the plate, was struck in the chest by a piece of a shattered bat. The incident occurred when Castillo lined a broken-bat double to left. The barrel of the bat flung into Colvin, who scored, but suffered a gash, and he was taken to the hospital.
The rookie was taken to Jackson Memorial in Miami, and his condition is stable. He is spending the night in the hospital, and he's out for the year with what is being called symptoms of a collapsed lung.
Marlins catcher Mike Rivera saw the play unfold in front of him.
"It was scary, seeing that part of the bat flying at him and hitting him kind of next to his heart," Rivera said. "It was pretty scary to see that."
It wasn't until afterward that Rivera learned that Colvin had been taken to the hospital.
"After he went to the dugout, I saw him run to the dugout with the trainer," Rivera said. "A thousand prayers to him, and hopefully everything is OK."
With a lineup of mostly rookies, the Cubs pulled off the lopsided victory.
"These kids are fun to watch," Cubs manager Mike Quade said. "They really gave us a lift today."
The Cubs seized control in the first inning, scoring twice on Bobby Scales' two-out, two-run single to center.
Everything unraveled for Florida in the second.
The Cubs sent 12 to the plate and scored six times. Miller and Brett Sinkbeil combined to walk six, and they threw 56 pitches in the inning.
"He hasn't been able to repeat his delivery," Rodriguez said of Miller. "That's the worse weakness on him. He has been fighting with that for a long time now."
Miller walked two in the inning, and he was replaced by Sinkbeil with the bases loaded. But the rookie walked the first three batters he faced in the inning.
Brad Snyder had a two-run single, which was his first big league hit, in the inning.
Samardzija held the Marlins without a hit until Uggla belted a two-run homer in the fourth inning. The other run allowed by the hard-throwing right-hander was Luna's pinch-hit homer with one out in the fifth.
The dozen walks, though, were too much to overcome.
"Obviously, it was the walks," Rodriguez said. "I don't mind if they throw strikes and they get hits. It was the walks. You can't defend the walks. That was the frustrating part."