MILWAUKEE -- A sellout crowd at American Family Field gave left fielder Isaac Collins a nice ovation in the second inning on Sunday, when the 27-year-old stepped up for his first career plate appearance. Collins was promoted from Triple-A Nashville on Sunday and was making his MLB debut.

The crowd grew louder moments later when Collins singled to center field, and then recorded his first stolen base on the next pitch. His debut was one of the few bright spots for the Brewers in Sunday’s 4-1 loss to the Rockies, as Milwaukee dropped its three-game set against Colorado. It marked a continuation of the Brewers’ slow start to September.

“It was a tough homestand,” manager Pat Murphy said.

The Brewers (82-61) are nine games ahead of the Cubs (73-70) in the NL Central after Chicago defeated the Yankees, 2-1, on Sunday afternoon. But Milwaukee is 2-5 to start this month and has lost back-to-back series for the first time since July 26-31, consecutive three-game sets to Miami and Atlanta.

The series loss to Colorado, which has the worst winning percentage in the NL (.375), follows the Brewers dropping two of three to the Cardinals this week. Milwaukee averaged 3.83 runs per game in six contests during the homestand, including Sunday.

Next up is a six-game road trip against the Giants and D-backs, which kicks off on Tuesday in San Francisco.

“Tough week,” shortstop Willy Adames said. “It’s just baseball. That's how it's gonna go. You're not gonna score 10 every time. I wish, but it’s not gonna happen. … We’ve just gotta move forward, and go to San Francisco and be better.”

Rhys Hoskins gave the Brewers an early lead with an RBI single off Rockies starter Kyle Freeland in the first inning. But after Collins’ single in the second, the Crew did not put a runner on base and finished the game 0-for-23.

Freeland, who also allowed a single to William Contreras in the first, was charged with one unearned run in six innings.

“It looked as though the Brewers were a little bit more aggressive than they were in the first couple innings, and that worked to Kyle’s advantage, too,” Rockies manager Bud Black said.

“The story of the game was Freeland,” Murphy said. “We had three singles. When was the last time this team has only had three singles in a game? A lot of balls in the air, not a lot of hard contact.”

Milwaukee recorded six hard-hit balls (those with 95+ mph exit velocities, according to Statcast). Only one went for a hit: Contreras’ single in the first (110.2 mph exit velocity).

The offense’s struggles gave starter Freddy Peralta little room for error, though the right-hander labored a bit. Peralta threw 86 pitches (50 strikes) before exiting after 4 2/3 innings, which marked his shortest start since July 6 against the Dodgers (four innings). Peralta, whose only clean inning was the second, was charged with three runs on seven hits and two walks.

“I think that I had more [to give],” Peralta said of the outing, before then adding of the Brewers turning it over to the bullpen: “That’s something that I cannot control.”

Peralta allowed a solo homer to Hunter Goodman to lead off the third. Two of the runs charged to him came after his exit. Murphy called on Hoby Milner in the fifth inning, after Peralta allowed consecutive two-out singles. The lefty surrendered a three-run homer to Colorado center fielder Sam Hilliard to give the Rockies a 4-1 lead.

“He's been so great for us this year,” Murphy said of Peralta. “We made a move that we thought was right, and it was wrong, obviously. The result was wrong, so that hurts, especially when you decide 4 2/3 innings in. He’s high-80s, 90 pitches, and you know he can go to 100. This is a left-on-left matchup, a veteran pitcher. It didn’t work out.”

The Brewers maintain a comfortable lead in the NL Central, but they’re heading into a difficult stretch of games. Including the upcoming road trip, Milwaukee will play Arizona seven times in a 10-day stretch. The D-backs (79-64) entered Sunday holding the NL’s second Wild Card spot.

Between those games against Arizona is a three-game home series against the NL East-leading Phillies from Sept. 16-18. That series could have implications for postseason seeding, as Philadelphia is 85-58.

“We have our work cut out for us,” Murphy said. “This was a week where we could have made up some ground and really done some things. We’ve got some great opponents [ahead].”