WASHINGTON -- Tuesday was a perfect opportunity for Marlins manager Don Mattingly and his staff to learn a lot about promising 23-year-old right-hander Zac Gallen. Until it wasn’t.

Less than a week removed from his second career start, also against the Nationals, Gallen was through two innings in D.C. on Tuesday before storm clouds engulfed Nationals Park and forced a 76-minute delay -- one that ultimately kept the youngster from returning to the mound in the Marlins' 3-2 walk-off loss to the Nats.

“You only pitch every five days, so you want to make the most of it when you are out there. It’s not fun when your outing gets cut short,” Gallen said. “We definitely had a little different idea of the game plan, and I wanted to see how it worked out. They had some new guys in the lineup that weren’t there a week ago.”

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It was an ideal situation for the coaching staff to see how Gallen absorbed that new game plan and how the rookie could mentally rebound against a team he had just faced that left him with a sour taste in his mouth.

In that first outing vs. Washington last Wednesday -- a seamless five innings followed by an unraveling in the sixth in his third time through the Nats’ lineup -- Gallen, overall, did his part to “show us that he has the weapons that he can pitch here,” Mattingly said before Tuesday’s game.

“There’s going to be a learning curve from game to game. Is it going to be consistency, start-in and start-out? This is another one of those series where he pitches against these guys, comes right back against [them]. We’ll see how the adjustments go.”

But Miami never got that chance.

“He’s going to learn plenty as the year goes on,” Mattingly said after the game. “You’re disappointed, because you don’t want to run through your bullpen on a rain delay.”

Even with a cheering section of 50-60 friends and family from New Jersey and Pennsylvania down the third-base side, there was never any discussion of Gallen toeing the rubber again.

“Didn’t feel good about sending him back out there,” Mattingly said. “He’s not really used to anything like that, so he’s too young for that for us. We have to be careful with him.”

Nearly four hours before Trea Turner stroked his walk-off RBI double, Gallen served up a two-run homer to Juan Soto in the bottom of the first on an 0-1 knuckle-curve. It came after the Marlins took the lead with three consecutive singles off Patrick Corbin to open the game.

On that long ball, right fielder Brian Anderson collided with the chain-link fence that shields the out-of-town scoreboard. He left the game in the second inning with a right elbow contusion, was replaced by Yadiel Rivera and is listed as day to day.

X-rays were negative for Anderson, and the hope is he can return in some capacity for Wednesday’s rematch.

With the bullpen doing its job, Miami fought back to tie the game in the eighth. Finally getting to Washington's woeful ’pen after being handled by Corbin for seven innings, a leadoff double from Cesar Puello was eventually cashed in on a sac fly from Miguel Rojas -- who was 3-for-3 and continued to torment the Nats -- after Puello had advanced on a groundout.

The combination of Adam Conley, Austin Brice, Nick Anderson and Jose Quijada held Washington’s potent lineup scoreless until Turner’s heroics on a ball in the gap off Quijada scored Yan Gomes, who had only reached after a “tough play” error on Neil Walker that Mattingly thought was undeserved.

But if there was any ray of sunshine for the Marlins in the otherwise cloudy affair Tuesday, it was the bullpen. Especially for Nick Anderson, who pitched his way into -- and out of -- a bases-loaded jam in the eighth to give his team a chance in the ninth, and Brice, who pitched three scoreless while conceding just a single hit.

“The story for us [is that] our bullpen was really good,” Mattingly said. “For the most part, [Brice has] been pretty efficient all year. … We felt pretty good about efficiency where guys weren’t getting beat up.”

But the pitching success only lasted so long -- and Gallen’s far shorter than that -- while Miami was forced to stomach its fourth consecutive loss to Washington.