"It's one of those days," Cubs manager Joe Maddon said. "You've seen him pitch really well. That's just a tough day for him there."
Maybe it's the Brewers. Montgomery served up a season-high seven runs and lasted 2 1/3 innings in his only other start against them this year on July 6. Saturday was his shortest start since he lasted 1 1/3 innings against the Athletics on Aug. 25, 2015.
"He's been pitching well overall," Maddon said. "Against this team, I'm seeing him not hitting the strike zone."
"Obviously, the command in the zone wasn't where I wanted it to be," Montgomery said. "It's one of those days. We have to move on. They're a good team and they play us really tough. They're giving us everything they've got out there. I have to do a lot better out there."
With the win, the Brewers moved to within three games of the Cubs in the National League Central standings.
"[A game like Saturday] reminds us that these guys don't look at us as the team to beat -- they think they're the team to beat and they come to play and act like it," Montgomery said. "It reminds us that we have to bring it against them."
Montgomery will get at least one more start on Thursday against the Mets, subbing for right-hander Jake Arrieta, whose return from a right hamstring strain is uncertain. Arrieta was injured last Monday against the Pirates.
Montgomery says he just has to forget games like the one he had Saturday.
"I might have been a little too fine, trying to make too good of a pitch, instead of just attacking the zone and trusting it more," Montgomery said. "That's baseball -- you have to go through that and learn from it. Going forward, I just have to be prepared for the next time and put the work in and focus on that."
Hopefully, he and the Cubs can avoid another inning like the Brewers' eight-run third on Saturday. It was the fourth time this season Chicago has given up at least eight runs in one inning, and all four instances have come against NL Central teams (one each against the Pirates, Cardinals, Reds and Brewers).
"It's just disappointing," Maddon said. "The big inning we've given up has really made for some awkward days for us this year."