Dunning, who said he was more of a Marlins fan than Braves fan growing up, allowed a double in a scoreless inning Sunday.
"It's a little different [in the Majors]," Dunning said. "It's the same game, it's just a little fierce now. I just have to keep the ball down and get a ground ball or something."
Dunning made his AT&T Park debut in the 13th inning of Monday's 5-3 loss. He entered the game after the Padres loaded the bases against Jose Mijares. Dunning walked home a run and recorded two outs.
"[It's a] small sample, but he came out and threw strikes in Atlanta," manager Bruce Bochy said. "We put him in a tough spot last night, but he controlled the damage. Sure, he walked in a run, but he settled down and got a big out."
Andrew Owens is an associate reporter for MLB.com. Follow him on Twitter @OwensAndrew. Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.