"It's bad, it's bad," Lee said. "There's no way around it."
Davis drove in two runs. Kouzmanoff extended his career-high hitting streak to 15. And the Athletics rebounded from a three-game sweep at San Francisco, taking this one after a 1-hour, 41-minute delay at the start.
"After a long delay, it's hard to keep your focus," Davis said. "Sometimes, you have a lack of concentration and focus, but the game is tough enough."
Lee, a three-time Gold Glove first baseman, committed back-to-back errors in a four-run fourth and right fielder Tyler Colvin added two more in a three-run seventh that broke open the game, making it 8-4.
"It's embarrassing," said Lee, who went 59 games without an error and had never committed two in an inning. "It's tough to let the team down like that."
All manager Lou Piniella could say was: "I've never seen Derrek do that."
Trevor Cahill (6-2) got the win despite allowing four runs and six hits over 5 2/3 innings, improving to 5-0 in his last six starts. He left after an RBI double to Chad Tracy that made it 5-3, and Jerry Blevins then gave up a run-scoring single to Koyie Hill that pulled the Cubs within one.
"I couldn't stop sweating," Cahill said. "It was hard to get a grip on the ball. And some pitches were getting away from me. It seemed like I went to rosin almost every pitch."
The Athletics regained control against Jeff Stevens in the seventh, although Colvin didn't help matters.
He let a single by Kouzmanoff get past him, putting runners on second and third with none out before Jack Cust walked to load the bases. Mark Ellis grounded into a double play, forcing the runner at the plate, but the Athletics got some more big breaks to pad their lead.
Stevens threw a wild pitch, allowing Kouzmanoff to score. Then, Cliff Pennington drove in Cust on a triple to deep right and scored when Colvin overthrew the cutoff man to make it 8-4.
Lee's errors in the fourth didn't help a shaky Carlos Zambrano (2-5), who gave up five runs -- two earned -- in six innings.
The Athletics already had a run in on Ellis' bases-loaded single in the fourth when Lee had his lapses. With one out, he came in on Cahill's roller and booted the ball, allowing Cust to score from third, and things were about to get worse.
Lee dropped the throw after shortstop Starlin Castro fielded Davis' chopper toward the middle as Ellis and Pennington scored to make it 4-0.
"I really don't know what happened, maybe it was in the dirt," Davis said.
Told the throw wasn't, he responded: "Wow, you don't expect that, but things just happen."
"That's unacceptable," Lee said. "They're weren't hard plays. I can't even tell you what happened. The way we're playing, I can't afford to do that."
The sloppy game came on the heels of one of the most memorable ones at Wrigley Field.
Athletics OF Conor Jackson, acquired from Arizona for minor league closer Sam Demel, went to left in the seventh and grounded out in the ninth. ... Oakland reinstated Suzuki from the bereavement list and optioned OF Matt Carson to Triple-A Sacramento. ... The four-error game was the most for Chicago since it had four against Cincinnati on Sept. 12, 2009. ... Colvin hit a solo homer in the eighth.