A couple of Marlins rookies made their MLB debuts on Saturday, and a lesson was clearly learned: There is little margin for error in the big leagues.

The Phillies homered four times and capitalized on nine walks, as they pulled away from the Marlins, 7-1, at Citizens Bank Park.

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“It seems like the walks were the theme for setting us up for trouble all day,” Marlins manager Don Mattingly said. “It could have been a lot worse, honestly. You walk nine guys in this ballpark, and it could have been a lot worse.”

Phil Gosselin’s first homer -- a go-ahead two-run blast in the sixth inning -- came against lefty Alex Vesia, who made his first MLB appearance. He is Miami's No. 27 prospect, according to MLB Pipeline.

Starter Caleb Smith labored through three innings, allowing just a Didi Gregorius homer, but he matched a career high with six walks, which also happened to be against the Phillies at Citizens Bank Park on April 5, 2018.

Nick Neidert, Miami's No. 10 prospect, settled things by throwing 2 1/3 scoreless innings in his MLB debut. He turned the ball over to Vesia with one out and no one on in the sixth.

“I think our brightest spot today was Nick,” Mattingly said. “He did a nice job in the middle there to get us to the back of the game. Ves gets his first out, and then he walks a guy.”

A 17th-round Draft pick by the Marlins in 2018, Vesia struck out Gregorius, the first batter he faced in the big leagues. But he walked Scott Kingery on a full count and Gosselin put the Phillies ahead for good with his homer to left-center.

Even though the game slipped away late, Neidert bridged the game from the fourth to the sixth inning, and the Marlins were in position to win. 

“We didn't come out with the win, unfortunately,” Neidert said. “We've always got tomorrow, but today was a very special day, and a dream come true.”

A starter throughout his Minor League career, Neidert’s first big league opportunity is coming in the bullpen out of necessity.

The Marlins split the first two games at Philadelphia, with a chance to take the series on Sunday.

“It was a dream come true,” Neidert said of his debut. “I dreamed of this day since I was 5 years old. I was the annoying kid in class who would actually stand up and say, 'No, I'm actually going to be a Major League Baseball player. The other kids would hate me for it. But it was an amazing feeling.”

J.T. Realmuto hit a three-run blast to center off Ryne Stanek in the seventh. In the eighth, Gosselin added a solo shot off southpaw Stephen Tarpley, who saw action with the Yankees the previous two seasons.

But the nine walks proved to be the biggest issue for the Marlins.

Of the 70 pitches Smith threw, 36 were strikes, and he relied on his offspeed pitches to get him out of some jams. In the second inning with the bases full, he froze Bryce Harper with a 2-2 curveball.

"Obviously, not a lot was working," Smith said. "Six walks in three innings, that's unacceptable. Fastball command wasn't there."