"Over the last month and a half, I think we've been firing on all cylinders," said Carroll, who stood in for Kazuo Matsui in his 15th start in the last 51 games. "We've lost five in a row.
"It's obviously something we've got to turn around and we don't want after playing well. I'm just hoping we can figure it out as soon as we can and get back to where we had been playing."
The skid coincides with the current road trip. The Rockies were swept in three games by the Blue Jays and will try to avoid being swept by the Cubs on Wednesday afternoon before beginning a four-game set with the Astros on Thursday night.
The rotation of, in order of appearance, Jason Hirsh, Aaron Cook, Josh Fogg, Jeff Francis and Lopez (4-1), is 0-3 with a 10.66 ERA on this trip, which will last 10 games. The struggles include 11 first-inning runs. Only Fogg threw a scoreless first.
"We've caused ourselves some difficulty playing from behind early," said Rockies manager Clint Hurdle, whose team also had a three-hit night from Willy Taveras. "They haven't been their best. They know that. They've been better and they'll get better."
Lopez gave up eight runs, including Cliff Floyd's two-run homer in the Cubs' three-run first inning, and nine hits in 4 2/3 innings. He had not given up more than three runs in any of his eight previous starts.
The starters have been dogged by two-out runs. The runs in the first and the Cubs' four-run fifth, which broke the game open, all occurred with two down. Lopez had escaped tight situations before Tuesday.
"I don't know how it's going to sound, but I feel like I had good stuff today. ... but things just didn't work out," Lopez said.
Cubs starter Ted Lilly (6-4) wobbled (6 IP, 6 H, 4 ER, 5 BB, 5 SO), but the Rockies couldn't knock him down.
The Rockies loaded the bases with no outs in the second, but scored only when Chris Iannetta grounded into a double play. After Carroll's two-run double in the fourth, Lilly forced a Troy Tulowitzki popup to end the inning with runners at the corners.
Carroll, whose homer came in the sixth and was his first of the season, doubled and scored in the ninth, and the Rockies had the tying run at the plate with no one out.
But Carlos Marmol struck out Tulowitzki and Matt Holliday, and Will Ohman earned his first save by forcing a Todd Helton popup.