Nicolino, making his second big league start, was touched for five runs on six hits in four innings. The 23-year-old lefty, who tossed seven shutout innings in his MLB debut in Cincinnati on June 20, wasn't sharp in his first outing at home.
"I made more mistakes," Nicolino said. "You can't do that up here. I left the ball up a lot more than I wanted to. It's something you learn from. You've got to battle. Tonight was one of those nights."
The Marlins are settling rotation spots. Nicolino made a strong first impression, which led to the start on Friday.
"He missed his spots a little bit," manager Dan Jennings said. "Just wasn't as sharp command-wise as he was the other day in Cincinnati. This is a good hitting ballclub. If you make mistakes up or in the middle of the plate, they're going to make you pay. I think he did that. We knew we had a fresh bullpen."
Cosart, making his first career relief appearance, is expected to eventually work his way back into the rotation. But since he hadn't pitched in the big leagues since May 13 at Dodger Stadium, he was being eased into action out of the 'pen.
The right-hander was reinstated from the disabled list on Thursday, after he dealt with vertigo. In four innings, Cosart gave up two runs on six hits with three walks and three strikeouts.
"He was amped up a little bit early, which is why we wanted to walk him through the bullpen," Jennings said. "It was certainly understandable. He's a young aggressive pitcher. I think he settled down very nicely late. He started getting his breaking ball over. He's an attack pitcher, and early he was a little amped up. That's expected."
Cosart said if he stays in long relief, he needs about 10-15 more warmup pitches.
"I just felt really out of sync, out of whack there in the [fifth] inning," Cosart said. "Then I settled down and made some pitches. My curveball felt really good."
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.