MIAMI -- Everything changed for Zac Gallen in a span of five pitches. That’s how quickly things can turn in the big leagues for a starter, especially when it comes to making it through a lineup a third time.

It’s a challenge for all starting pitchers, and the third time through the order proved crucial on Wednesday night in the Marlins’ 7-5 loss to the Nationals at Marlins Park.

Matt Adams’ three-run homer off Wei-Yin Chen capped a four-run sixth inning, and Patrick Corbin limited Miami to one run over seven frames.

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In terms of the overall growth from Gallen, Wednesday was very encouraging, as well as educational.

“Overall, you kind of make a call when you have a young guy like that,” Marlins manager Don Mattingly said of the club's No. 18 prospect, as ranked by MLB Pipeline. “Do you let him have the five innings and get him out of there, and leave it positive? Or do you let him keep growing? Obviously, it didn't go good today at the end of that. I'm sure he's going to learn from it, and go from there.”

The main takeaway, Gallen said, was he better understands that making it deeper into games will require being more economical with his pitches and pitch effectiveness. Through five innings, he was at 86 pitches.

“I feel like I used too many pitches,” the 23-year-old Gallen said. “I would have liked to have gotten to the sixth with less pitches. But other than that, I think it was OK.”

Trailing by six runs entering the ninth inning, the Marlins closed the gap on Bryan Holaday’s RBI single, and Curtis Granderson added a three-run triple.

The Nationals have taken the first two games in the series, and Gallen took his first big league loss.

“He's got good stuff,” Nationals manager Dave Martinez said. “His slider was good. He kept the ball down. We finally got the ball up in the zone, and we had one inning where we had three hits -- boom, boom, boom. He has really good stuff. I'm just glad that we were able to get him up a little bit and start hitting the ball.”

Gallen, making his second start since being promoted from Triple-A New Orleans and first at home, struck out eight and allowed one hit through five scoreless innings to open his night. In the process, he had a stretch of fanning six of eight batters from the third inning through the fifth.

With three starters on the injured list, Gallen is getting his first big league opportunity to see if he can stick in the Marlins’ rotation. In his first two starts, he’s made it through five innings both times. He has logged 14 strikeouts in 10 innings, and just nine hits and four runs.

But a byproduct of high strikeout totals can be high pitch counts. In Gallen’s first start, on June 20 at St. Louis, he fanned six in five innings and was replaced after 99 pitches. His start took him into the sixth inning Wednesday without recording an out, when he finished up at 91 pitches.

Gallen even helped himself, with a single off Corbin in the third inning. It was his first big league hit, and he scored on Harold Ramirez’s RBI single.

Interestingly, Gallen pitches wearing glasses, but doesn’t wear them when hitting.

“The glasses are only because, at nighttime, I can't see the signs,” Gallen said. “My astigmatism and the shadows. ... I probably could use them for hitting, but I don't wear them every day. It throws me off even more.”

Clinging to the one-run edge, Gallen came out for the sixth inning at 86 pitches, which was likely going to be his final inning, no matter the result. Chen already was warming up in case Gallen labored.

“I think they started jumping on him the third time through,” said Holaday, who also caught Gallen earlier in the season with New Orleans. “It seemed like they got a little bit more aggressive, they didn't want to get deep into counts. He did a great job overall. He went out there and competed. That's how it goes sometimes.”

Three pitches into the sixth inning, Trea Turner singled on a 91.9-mph four-seam fastball. The exit velocity was recorded at 99.5 mph. Adam Eaton then jumped a first pitch from Gallen and singled to center, putting runners at the corners. And Anthony Rendon was all over a first-pitch, 87.4-mph cutter, delivering an RBI single to left. The exit velocity on Rendon's hit was 102.8 mph.

“I think ultimately, when you get through the lineup a third time, guys have seen enough pitches, and they don't want to get to two strikes or deeper in the count,” Gallen said. “I think they just ambushed a few pitches. Probably better pitches would have been early outs.”

Gallen was lifted at 91 pitches. Chen inherited two on and no outs, and struck out Juan Soto. But Adams’ three-run homer was the deflating blow. It made the score 4-1, with three earned runs charged to Gallen.

Gallen’s line was five-plus innings, allowing four hits, two walks and striking out eight. Of his 91 pitches, 59 were strikes.

“I thought he did a nice job of basically keeping them a little off balance,” Mattingly said. “I thought actually his [sixth inning] was one of his better innings. We committed to go through Rendon there.”