Miley was easy to overlook, despite having appeared in eight games for the D-backs in 2011, and he seemed a long shot to make the team at the start of the spring.
Miley even had his car all but packed to head to Triple-A Reno when he found out he had made the team. And it wasn't until he pitched well out of the bullpen that he was given a spot in the rotation.
So what was it that Montero saw in Miley?
"I saw that hunger on his face and he was fearless, so it caught my eye," Montero said. "I knew he was going to have a good year."
In a way, Montero's prediction was off the mark. Miley didn't have a good year; he had an exceptional one. He was the lone D-backs player selected to make the All-Star team and he wound up going 16-11 with a 3.33 ERA in 32 games (29 starts).
Miley wound up finishing a close second to the highly-touted Bryce Harper in the National League Rookie of the Year voting.
"He ain't afraid of nothing," Montero said. "He just goes out there and goes after any hitter. Guys who try to pitch around guys or are scared to get hit get into trouble. He wasn't scared of any of that. It shocked me, because when you see that on somebody's face you have to keep your eyes on them because he's a guy you should be afraid of as a hitter."
Miley receives a lot of good-natured teasing from people for some of the things he says -- like saying he hoped to visit Alcatraz Island while the team was in San Diego last summer -- but rest assured Miley is not dumb.
In fact, it could be argued that he's got the smartest approach of anybody on the team because of how he manages to keep things simple.
For instance, rather than worry about what type of pitch to throw a hitter, Miley will let Montero decide that and he'll focus all his attention on making the pitch a good one.
"Miggy's good," Miley said. "I haven't thrown to many catchers comparable to him in terms of his plan and what he wants to do during a game. He's been here for five or six years, he's seen the guys around the league and knows their strength and weaknesses, so why not trust him? It doesn't matter what type of pitch you throw. As long as you make a quality pitch, I think you'll have success."
It's that kind of mental approach that has D-backs general manager Kevin Towers and manager Kirk Gibson believing that Miley will not experience a letdown from last season.
In fact, mention the dreaded "sophomore slump" to Miley and he'll shake his head.
"Why think about that?" he said. "That's my answer. Why even put more pressure on yourself? I just want to go out and pitch. I'm not going to try and do what I did last year. I'm going to go out and pitch and try to help my team win every five days. I'm just going to pitch like I've done my whole life."
Miley credits his ability to focus strictly on the task at hand to Jay Artigues, his coach at Southeastern Louisiana University.
Artigues drilled it into Miley's head that the only thing he could control was the pitch he was throwing at that time, so to give that his full attention. The lack of worrying about things other than throwing the pitch his catcher calls allows Miley to work fast.
"I try not to turn my back on the catcher," Miley said. "Just get it and go. Your defense plays better and the guys you're facing don't like it. Why not use that to an advantage."
If Miley does slip, he has Montero there to keep him on track.
Earlier this spring, Montero noticed Miley thinking too much on the mound and saw that his mechanics were not as good. Prior to Miley's next bullpen session, Montero pulled him aside.
"I said, 'I really don't want you to think right now because you're a guy that doesn't think,'" Montero told him. "'You just go out there and let it go.' As long as he stays healthy and stays on top of his body and in shape, he could be even better with experience."
Miley recently had a brief bout with a "dead arm" period that pitchers typically go through at some point during the spring, but after skipping a start, he appears to be back on target to start the season on time.
"I just hit a wall, but I feel great now," Miley said.