PHILADELPHIA -- Prior to Monday's series opener against the Brewers, Phillies manager Gabe Kapler acknowledged that this would be a "very challenging stretch" for his club.

The four-game set with Milwaukee kicked off a 23-game stretch in which the Phillies would exclusively face fellow National League contenders -- the Brewers, Rockies, Cubs, Cardinals, Dodgers and Padres. Despite getting off to a promising start with a come-from-behind victory on Monday, Philadelphia dropped a third straight game -- and the series -- in an 11-3 loss on Thursday at Citizens Bank Park.

The three straight losses match a season-long streak for the Phillies, who also dropped three in a row from April 21-23. They were outscored 22-6 after winning Monday's opener.

• Box score

“They just outplayed us from every angle," Kapler said. "They pitched better, they swung the bats better, they played better defense, they made more pitches, they got more hits. It’s that simple -- they just outplayed us.”

Zach Eflin, who was coming off his second complete game of the season, allowed four runs off seven hits and two walks, while striking out seven over five innings. The four runs were double the amount he had allowed over 25 innings in his last three starts. It was also one more than Eflin had given up in 23 previous innings at Citizens Bank Park this season.

After allowing a first-inning homer to Christian Yelich -- who would add another home run in the eighth inning to extend his Major League-leading total to 18 -- Eflin allowed one run each in the third, fourth and fifth innings. He was just the latest Phillies' starter to run into trouble against the Brewers, as Philadelphia's starting rotation combined to allow 17 runs (16 earned) over 18 innings in the four-game series.

“We have to play very good baseball to beat teams like Milwaukee, Colorado and Chicago," Kapler said. "We don’t have the margin for error. Most teams don’t. When you go and play the best teams in the league, you have to play your best baseball, and we certainly didn’t in this series."

Offensively, the Phillies tried to shake things up by swapping Bryce Harper and Jean Segura in the batting order. Harper, hitting second for the first time this season, went 1-for-4 with a strikeout, though all three balls he put in play had an exit velocity of at least 99 mph, according to Statcast.

Segura, meanwhile, hit a first-inning homer out of the three hole -- just as he had done one day earlier hitting second. The Phillies, however, would manage just three more hits and a pair of unearned runs on a Segura RBI groundout and a Rhys Hoskins sacrifice fly.

“What we have to do is go back and look at it from every angle, and examine it carefully, then make adjustments," Kapler said. "Action steps have to come following a series like this. You can’t just kind of sit on your hands and hope it’s going to get better for the next series. You have to take action steps, and we’ll do that.”

As for what exactly those steps might be, Kapler said those answers aren’t readily available immediately following a game. He called it a process, one that involves watching video, examining the numbers and having more conversations with his staff.

Veteran outfielder Andrew McCutchen, who had the Phillies' only other extra-base hit with a double, summed up the series in much simpler terms.

"If you don’t do your job, you’re going to get your butt kicked," McCutchen said. "That’s plain and simple. You play good ball and you win. We can all agree here that we didn’t play our best baseball and in return, we got our butts kicked."