MILWAUKEE -- The stage was set for the Chicago Cubs to break a five-game losing streak and gain a game on the first-place Milwaukee Brewers, but after taking an early 7-0 lead on Wednesday, the Cubs became just the second team since 1900 to score seven or more runs in the first inning, only to lose by at least that many.

"A bad ending to not our best road trip," Cubs manager David Ross said after the 15-7 loss.

The Brewers scored a run in the first, five more in the second and then put up eight in the fourth -- the final four of those runs coming on a Willy Adames grand slam. Luis Urias then added another home run in the sixth -- his second of the game.

"I don't know what to say," Adames said. "This one was crazy."

Cubs veteran pitcher Jake Arrieta couldn't hold on to the lead and was pulled after just 1⅔ innings. The loss dropped the Cubs six games behind the Brewers after the two teams were tied for first in the NL Central just a week ago. Milwaukee has won eight in a row, while Chicago has dropped its past six games after throwing a combined no-hitter against the Los Angeles Dodgers last Thursday.

"I think first place can go up and down before September," Cubs shortstop Javier Baez said. "I'm not worried about that. Javy Baez is not worried about that. I'm not paying attention to that. We're playing against pretty good teams."

The Cubs completed a brutal month in terms of both travel and playing elite opponents. The result was a 12-16 record and a franchise-worst (since 1900) .1875 batting average in a calendar month. They hit .188 in April 1944.

Their current position in the standings might determine the direction of the front office with a month to go before the trade deadline. Ross knows the Cubs have something to prove to team brass. They have more than 10 players set to become free agents after this season.

"The key is for us to represent a winning product and something that can win a division and go into the playoffs and do something special," Ross said.

The Brewers, meanwhile, have opened up the largest lead of any first-place team in baseball this season. According to ESPN's win probability tracker, they had a 4.7% chance of winning Wednesday's game after the first inning -- but that jumped to 99% by the start of the fifth.

"It's why we love the game, at least on this side right now," Brewers manager Craig Counsell said. "You come into these series and sweeps change the landscapes pretty fast. It can change just as fast the other way."

The Cubs find themselves in rare company. On April 26, 1976, the Giants scored seven runs in the first inning and also lost 15-7.

Over the past 20 seasons, according to ESPN Stats & Information research, there have been 8,691 instances of a team leading by seven runs at any point in a game. Entering Wednesday, only two of those teams had lost by eight-plus runs. Now there are three.

"When you're going to the bullpen in the second or third inning, it's going to be tough to win those games," Ross said.

As the calendar flips to July, Milwaukee is seemingly in command of the NL Central, but Counsell is cautioning patience for a long season.

"Nothing is decided," he said. "When you give yourself some space you give yourself a little room for error. We know there is a huge number of games left still. Nothing has happened this week. We have to continue to play good baseball."

According to Elias Sports Bureau research, Brewers rookie Aaron Ashby is the first starter since the mound went to its current distance in 1893 to pitch fewer than one inning and allow at least seven runs in his MLB debut. Ashby was pulled after ⅔ of an inning, while the Cubs sent 12 men to the plate. It turned out not to be enough offense for the visitors.