Despite how well he worked on the mound in his first MLB start, Kyle Muller’s most impressive moment of the day might’ve come with a bat in his hand.

In the third inning of Monday’s 4-2 loss in Game 1 of a straight doubleheader at Citi Field, Muller stood toe-to-toe with the National League Cy Young favorite, Jacob deGrom. Though deGrom had retired his first eight batters, Muller worked an eight-pitch walk — his first time on base in the Majors.

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Muller fouled off a 100.5 mph fastball to stay alive at 0-2. He then watched three high sliders sail by, fouled off another heater and took a final slider for ball four. The Braves managed just three baserunners in five innings against deGrom, and against the odds Muller was one of them.

“I don’t want to act like that was all skill; there was definitely luck involved there,” Muller said. “If he’d thrown the good [slider] that he threw to every one of our hitters, it might’ve been a different story. I was pumped.”

Atlanta’s No. 5 prospect also impressed in four innings of work on the mound, striking out three while allowing one run on a hit and two walks. The run came during a jumpy first inning, when Muller walked the leadoff batter and later allowed him to score on a wild pitch.

The only hit against Muller came in the second on a bad-break double that bounced off outfielder Guillermo Heredia’s glove. Muller threw another wild pitch in that frame, but it didn’t cost him. And after walking against deGrom in the next half-inning, he retired his final six batters.

“I thought I did a way better job today than the other day of executing pitches with two strikes, and that was huge,” said Muller, who allowed two runs in his one-inning MLB debut last Wednesday.

Pitching against baseball’s most dominant pitcher was surreal for the 23-year-old Muller, who walked out to the mound several hours before the game “so it wasn’t foreign to me when I got out there.”

He looked up at the stadium’s big screen and saw his face next to deGrom's, with their lopsided season stats on display.

“I wanted to take a picture of it so bad,” Muller said. “But I was like, ‘No, don’t do that. Act like you’ve been here before.’”

Muller looked like he’d been there before with the strong outing that followed, though his offense couldn’t hold up its end. Ozzie Albies’ two-run homer in the sixth produced the Braves’ only offense. Albies now has 12 extra-base hits and 18 RBIs in his past 19 games.