PHILADELPHIA -- Maturity on the mound is coming in stages for Pablo López.

The promising 23-year-old right-hander on Sunday was starting to get a grip on his up-and-down outing in the sixth inning when he lost the feel for his offspeed pitches. An errant breaking ball plunked Bryce Harper on the foot, and a poorly executed changeup led to a run scoring a wild pitch.

In many ways, the sloppy sixth inning epitomized the Marlins’ struggles in a 5-1 loss to the Phillies at Citizens Bank Park.

“We always try to limit free bases -- hit by pitches, walks, all those things,” Lopez said. “It came back to get me today -- those two walks, those free men on base. Just try to limit giving those free bases.”

The Marlins ended up dropping three straight after taking the four-game opener on Thursday, and finished 2-4 on the road trip.

“Disappointing after the first game,” Marlins manager Don Mattingly said. “That’s pretty much the whole thing, for me. You win Game 1 of a four-game set, you should be able to get a split out of that if you pitch well.”

Miami liked its chances heading into the series finale, especially with Lopez coming off a strong 6 1/3 innings in a win at the Indians on Tuesday. He allowed one unearned run on two hits in that contest.

“From my perspective, Lopez was efficient,” Phillies manager Gabe Kapler said. “And I watched him right before the game, and it looked like it was going to be a really tough afternoon [for us]. I even shared that with some people.”

But on Sunday at Philadelphia, Lopez had trouble getting into any consistent rhythm.

In the first inning, he logged two quick outs, but walked Harper and then surrendered an RBI double to Rhys Hoskins, who blistered a two-seam fastball into the gap in left-center, capping a nine-pitch at-bat. Lopez labored through 26 pitches in the inning.

“I happened to fall behind to some guys, they walked, and ended up scoring,” Lopez said. “That's where getting ahead and staying ahead comes into play, so you can keep a tempo, and keep a rhythm of the game going, and not allow the other team to kind of create something.”

Still, he rebounded for a clean, 10-pitch second inning, before running into trouble again in the third when he needed 20 more pitches to get through the inning. Jean Segura had an RBI triple and Harper added a run-scoring groundout, giving the Phillies a 3-0 lead.

After Miami scored in the fourth on Miguel Rojas’ RBI single, Lopez settled in again with two quick innings, including fanning the side on 10 pitches in the fifth.

In the sixth inning, it was clear from the start that Lopez had lost the feel for his curveball. Two of them almost hit Segura, who ended up reaching on a single. Harper was then hit by a pitch, but Lopez still had a chance to get out of it. He got Hoskins to bounce into a 5-4-3 double play, with Segura advancing to third.

Yet Lopez's wild pitch on a changeup allowed Segura to scramble home to make it 4-1, and Lopez’s afternoon was over after he walked Nick Williams.

The Marlins felt they got squeezed on a 1-2 changeup to Williams -- which would have been an inning-ending strikeout had it been called a strike -- prior to that fourth run scoring on the wild pitch. But home plate umpire Dan Iassogna called it a ball.

“If we punch Williams out, the run he gives up there [doesn’t score],” Mattingly said. “Then he tries to go down with the changeup, and it just gets away.”

Lopez took the non-strike call in stride.

“It would have been nice to get the call, but at the same time, it's part of the game,” Lopez said. “It's out of my control. My job is to execute the next pitch, and I certainly didn't. That's what happens.”

The way Zach Eflin threw for the Phillies, the Marlins had little room for error. Eflin tossed his third career complete game.

“We put some good at-bats together,” said Lewis Brinson, who had one of seven Miami hits. “We just couldn't get anything going when we needed it. Eflin pitched a great game. Had his stuff working, kept us off balance. We just couldn't get anything going.”

Lopez, one of the core rotation pieces the organization is building around, finished with 94 pitches, including 60 strikes. So it wasn’t so much he was wild all afternoon, but he walked three, struck out four, and matched his season-high by giving up four runs.

“Pablo was actually pretty good,” Mattingly said. “He got his pitch count back together early on, and kind of got himself back in line in the fourth and the fifth. At that point, it's 3-1, we're in the game.”