Reliever Kerry Wood had no margin for error when he entered in the eighth. It's been that way every game so far this season for the Cubs.

Wood gave up a two-run homer with two outs to pinch-hitter Casey McGehee and the Cubs lost 6-5 to the Milwaukee Brewers on Sunday to drop the series.

Only one of Chicago's first nine games has been decided by three runs or more, a 6-0 loss on Saturday to Milwaukee, and the Cubs are 2-4 against NL Central foes.

"It's not easy. You keep thinking they're going to bounce your way eventually, you're going to get some breaks," Wood said. "We've got to win that game, win that series. No question. It didn't happen."

The Cubs certainly had plenty of opportunities after Brewers starter Yovani Gallardo labored through five innings.

Milwaukee's bullpen also ran into trouble in the seventh, with relievers Sean Green, Mitch Stetter and Kameron Loe each allowing a runner to load the bases with one out. Tyler Colvin's RBI groundout off Loe (1-0) gave the Cubs a 5-4 lead.

"When you've got a guy like Gallardo on the ropes, you need to put them away. It ain't that easy but yeah, we had plenty of chances," Cubs manager Mike Quade said. "It's a lot easier for everyone if we can find a way to give ourselves a cushion of more than a run. Obviously, you make one mistake in this ballpark with their club offensively and everything else, it's a tough deal."

Prince Fielder and Ryan Braun each hit a two-run homer for Milwaukee, which has won five of six after an 0-4 start. Worse, McGehee had been mired in a 3-for-22 slump this homestand and didn't get the start. Wood (0-1) walked Yuniesky Betancourt to open the eighth and Betancourt reached second on a sacrifice bunt.

After George Kottaras struck out, McGehee hit the second fastball he saw into the Cubs' bullpen in right.

"We know we're going to play tight games. That's part of it," Wood said. "You start the inning off with a walk, you put yourself behind the 8-ball."

Chicago's Aramis Ramirez drove in three runs on three doubles. He started this road trip that continues Monday in Houston 1 for 8 before doubling down the left-field line in the first inning to drive in two.

Fielder tied it in the bottom of the first with his second homer and is 11 for 18 with two home runs and 11 RBIs in the last four games after failing to knock in a run in a 3-for-17 start.

Chicago added runs in the second on Darwin Barney's RBI single and the third on Ramirez's run-scoring double to put the Cubs up 4-2, but Milwaukee tied it again on Braun's two-run shot off Casey Coleman in the bottom of the third.

Coleman got the start because Randy Wells (right forearm) is on the disabled list.

Cubs right fielder Kosuke Fukudome saved a run in the second with a diving catch for the third out and made a shoestring grab with two on and one out in the fifth to keep the game tied.

After doubling for the third time in the fifth, Ramirez was thrown out at the plate when third baseman Craig Counsell went home with Geovany Soto's slow roller to set up the back-and-forth finish.

"We're just not giving ourselves much room for error," Quade said.

NOTES: Coleman hit his second career double in the fourth. ... With a day off on Monday, Brewers RHP Takashi Saito (hamstring) is not expected to go on the disabled list despite his nagging injury. ... Cubs OF Alfonso Soriano also was out of the starting lineup, but pinch hit in the sixth for Fukudome, who left with a mild hamstring strain and is day to day. ... Brewers LHP Manny Parra (back) will report to Triple-A Nashville on Tuesday for his second rehab start.