CHICAGO -- One of the hallmarks of any Joe Maddon-managed team that has played deep into the postseason has been sound defense, which, when coupled with effective starting pitching, has produced favorable results.

In their first three games since the All-Star break, the Cubs had exhibited clean play in the field, which translated to a three-game winning streak. But when the defense broke down on Monday night, namely in the seventh inning, the tide suddenly turned, and the Cubs were strapped with their first loss of the second half in a 6-3 setback against the Reds at Wrigley Field.

• Box score

The Reds tallied five runs in the sixth, seventh and eighth innings, and the Cubs’ defensive miscues played a role. Maddon called the errors uncharacteristic and doesn’t expect defensive sloppiness to be an issue moving forward, but for the first time since the break, such liabilities were at the center of a loss.

“We did not make some plays, and that was it,” Maddon said. “I have no answers. We had opportunities to score a lot more runs. That’s really what it comes down to, I think.”

Third baseman David Bote was charged with the second error of the Reds’ two-run seventh when Eugenio Suarez lined a sharp grounder that skipped off Bote’s glove. The error allowed the go-ahead run to score.

Earlier in the seventh, after Curt Casali tied the score at 3 with a home run on the first pitch he saw from reliever Steve Cishek, Javier Báez couldn’t field what appeared to be a double-play ball, extending the inning.

Maddon said the Casali home run changed the dynamic of the game.

The Reds tacked on a pair of insurance runs in the eighth. Kyle Farmer drove in a run with a double that came immediately after first baseman Anthony Rizzo and catcher Victor Caratini allowed Farmer’s pop foul to drop between them. Michael Lorenzen extended the lead to three runs with another RBI single.

The Cubs put two runners on in the eighth, but Reds closer Raisel Iglesias got pinch-hitter Albert Almora Jr. to line out to third, and Addison Russell was doubled up off second base.

Leading, 3-2, in the sixth inning, the Cubs had a prime chance to extend the lead when they loaded the bases with only one out. But after Rizzo doubled, Jason Heyward singled and Russell walked, Reds starter Luis Castillo struck out Bote and pinch-hitter Robel Garcia.

Castillo struck out 10 over six innings in a game in which the Cubs left nine runners on base to go along with the two costly errors.

“We had chances to score runs, man,” Maddon said. “It could have been an entirely different game, and then the bullpen would have been used differently at the end.

“It was closer than it actually looked. We made mistakes to compound the issue.”

The Cubs snapped a 1-1 tie in the fourth inning with a pair of runs following a Kris Bryant walk and a Rizzo double. With one out, Bryant scored on a Heyward groundout, then Rizzo scored when a Castillo pitch skipped away from Casali behind the plate.

Trailing by one in the third inning, the Cubs drew even on Kyle Schwarber’s 20th home run of the season.

Starter Kyle Hendricks pitched six strong innings, allowing two earned runs while striking out five. Despite allowing two home runs -- one in the first to Suarez and one to Puig in the sixth -- he said he felt more like himself as he recorded his ninth quality start of the season. He allowed just four hits overall.

“It comes down to keeping the same focus and making good pitches,” Hendricks said. "Today I just made two pitches I didn’t get away with.”