Seattle's Jeremy Bonderman took the loss as Alfonso Soriano and Darwin Barney each doubled twice to help the Cubs build a six-run lead before holding off the Seattle Mariners 7-6 Sunday.
Anthony Rizzo drove in two runs and the Cubs tied a season high by hitting six doubles.
Chicago led 7-1 after four innings. The Cubs' bullpen, which has blown 16 save chances this season, gave up three runs in the eighth.
Kevin Gregg pitched a hitless ninth for his 13th save.
Edwin Jackson (4-10) pitched into the seventh inning, allowing three runs and seven hits and striking out six.
Jason Bay homered for the Mariners and Brad Miller doubled twice for his first major league hits .
Bonderman (1-2) was chased after giving up six runs four earned and six hits in 3 1-3 innings. It was his shortest start since going 2 1-3 innings on July 29, 2007 with Detroit.
The loss was the first for Bonderman since being called up June 2 and making his first major league appearance since 2010. That time out, he gave up seven runs in 4 2-3 innings, but since he had been on a roll, giving up a total of four runs in the four starts before Sunday.
Bonderman's trouble against the Cubs started in the second inning when the Cubs doubled four times, leading to three runs. Soriano and Rizzo led off the inning with doubles, and with one out Brian Bogusevic and Barney hit consecutive RBI doubles.
In the fourth, Barney led off with another double and scored when Wellington Castillo's grounder to third went through Kyle Seager's legs for a two-base error. Starlin Castro's run-scoring single marked the end for Bonderman.
Reliever Blake Beavan gave up an RBI double to Soriano and another run on Rizzo's single as the Cubs took a 7-1 lead.
Beavan settled down and pitched through the eighth inning. The Cubs only managed one hit over the final five innings.
The Mariners' comeback started in the fifth when Nick Franklin's single drove in a run. Bay's leadoff homer in the seventh cut the lead to 7-3.
Raul Ibanez led off the eighth with his 19th homer of the season. Kendrys Morales singled and Seager broke an 0-for-19 slump with a deep home run down the right-field line to bring the Mariners within a run.
NOTES: Cubs OF Ryan Sweeney will be placed on the disabled list after breaking a rib on his left side crashing into an outfield wall. Sweeney will be held out of baseball activities for four to six weeks. ... Seattle CF Dustin Ackley should be able to return "in a couple days" after spraining his right thumb Saturday, manager Eric Wedge said. "All things considered, could be a lot worse," Wedge said.