Conley did nothing to hurt his chances on Friday in his Grapefruit League debut in the Marlins' 5-4 walk-off win over the Nationals at Roger Dean Stadium.
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In two innings, Conley pounded the zone, throwing 13 of 17 pitches for strikes. His fastball reached 94 mph. The blemish was surrendering an opposite-field home run to Michael Taylor in the second inning.
Other than that, he got soft contact, once breaking Trea Turner's bat in the first inning on a 6-4-3 double play.
"Adam has been great," Marlins manager Don Mattingly said. "He's been all business. He's straightforward. He's been aggressive. He goes about his work. He's just fighting. It's all good."
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Conley, 4-1 with a 3.76 ERA in 67 innings last season, is in the mix for one of two rotation spots.
Still with options, the Marlins may decide he needs more Minor League seasoning, but that may change.
"If I do go down to Triple-A, it's not going to deter me from my ultimate mission, which is to make my stuff the best it can be -- hide the ball longer, be more deceptive, throw the ball with more power," he said. "Take better care of my arm, my brain, my body, all of those things. That process won't ever change, no matter what level I'm at."
Conley opened last season at Triple-A New Orleans, but he ended up appearing in 15 games with 11 starts for the Marlins.
This is Conley's fourth big league camp, and the first in which he has a realistic chance to make the Opening Day roster.
"If you just look at a guy's chances of trying to make the Opening Day roster when he doesn't have a day in the big leagues, it's not likely to happen," he said. "Jose Fernandez, you look at that guy. He had not pitched a day above A ball, never pitched in the big leagues. Makes the team and wins Rookie of the Year. That's an outlier stat.
"Every talented young player that comes up, that doesn't happen to him. He's a very special guy in that way."
The general feeling with Conley is he is on the cusp of being ready. What the organization hopes for is when he is part of the rotation, he is in the big leagues to stay.
"I've always believed I could pitch in the big leagues," he said. "That's not a feeling that's come to me recently, that's something I've believed in myself for a long time."