Allowing only two runs on nine hits, Bush (5-7) put together his fifth consecutive quality start. He was in control for most of the night, allowing only one hit through the first four innings.
"I thought I threw pretty well tonight," Bush said. "But I needed to be one better."
The game turned on Bush in the fifth, though, when the Cubs tied the game at 1 on a Matt Murton triple that scored Michael Barrett. Ronny Cedeno then hit a sacrifice fly to score Murton and give the Cubs a one-run advantage.
The Cubs jumped on Bush early in the count in the inning, as he threw only 12 pitches to seven batters.
"Most guys, when they're going to attack, they're going to attack on a fastball," Bush said. "They'll try to swing at a fastball early. I don't think that was necessarily the case today."
Brewers manager Ned Yost said he was pleased with how Bush attacked the plate in the first four innings. Bush said the game probably turned on four pitches in the fifth, in which the Cubs scored the eventual game-winning runs on four hits.
"I don't think it was a situation of being ambushed," Bush said. "They just strung them together and gave themselves a chance to score from third base with no outs. That was a pretty good situation for them."
Once again, though, Milwaukee's offense couldn't make up for a bad inning by its starter. In the first, the Brewers loaded the bases against Cubs starter Carlos Marmol (2-3), but Bill Hall struck out to end the threat.
"He throws that just-high-enough fastball," Hall said. "It's tough to hit and put in play. It looks good to hit, but it has enough on it that you can't catch up to it."
It was the second straight game Hall -- known this season for his ability to come through at the plate when the Brewers need it -- could not drive in a run with the bases loaded.
"I thought I could help myself at the plate. I take pride in swinging the bat. I was trying to give ourselves a little bit of an advantage."
-- Dave Bush
Hall now has struck out in 22 of his last 53 at-bats, including two punchouts in an 0-for-4 Saturday.
"He's just off right now," Yost said. "Just off somewhere in his swing."
The Brewers may have had a bit of a hangover from the sixth inning Friday night, when they loaded the bases against the Cubs' Carlos Zambrano but came away with just one run.
"The wind came out of our sail a little bit after that," Jeff Cirillo said. "Tonight we had a lot of opportunities early, and it was the same thing. Our pitching's been pretty good; unfortunately, their pitching has been a little better."
Early on it appeared the Brewers would get to the Cubs' bullpen early, as the Brewers worked deep into the count on Marmol, forcing the Cubs right-hander to rack up a high pitch count.
Bush even came through for his team at the plate, driving in the Brewers' lone run with a double in the second that scored Damian Miller.
It was all good news early for the Brewers, especially having scored first. In the previous 15 Cubs-Brewers meetings, the team that scored first won the game. But with Bush notching the only Brewers RBI, that streak came to an end.
"Bush is the only guy that came up with an RBI tonight, and that doesn't bode well for us," Cirillo said. "I thought we worked counts well, made [Marmol] throw a lot of pitches. We just weren't able to get the big hit."
On his third RBI of the season, Bush added: "I thought I could help myself at the plate. I take pride in swinging the bat. I was trying to give ourselves a little bit of an advantage."
With the loss, the Brewers now need a win to finish at .500 at the All-Star break. Last season, they were four under .500 and 14 games out of first place at the break. Now they sit 4 1/2 games out of first, but Yost has at least one clear goal for the second half that his team must accomplish in order to seriously compete for a playoff spot.
"Our offense has probably been more inconsistent than consistent," Yost said. "When we're swinging the bat well, we seem to be doing it over a period of time, and when we're not swinging the bats well, we're not swinging well over a period of time. I think we need to strive to be more consistent in the second half."