But minutes before he was set to take the mound at Coors Field on Saturday to face the Cardinals, the National League's top hitting team, the nerves began to settle in.
"I was just joking with him, because he was in [the clubhouse] walking around, and I'm like, 'That guy is real nervous,'" center fielder Dexter Fowler said.
Once he started firing fastballs, though, Nicasio looked more like the relaxed guy in the chair than the one pacing the clubhouse.
Nicasio, 24, pounded the strike zone relentlessly on his way to seven innings of six-hit, one-run ball, and that run was unearned. Complemented by the Rockies 18-hit explosion in a 15-4 victory, it was more than enough for Nicasio to earn his first win in the Majors.
Nicasio arrived in Denver from Double-A Tulsa on Thursday, and he spent much of the last two days talking to other starters on the Rockies staff, trying to glean some advice on what to expect in his first big league start.
"I got advice from other pitchers to just go out and attack the strike zone," Nicasio said, as fellow Dominican Ubaldo Jimenez translated. "I made sure I threw everything down in the strike zone."
Nicasio gave up a hit to the first batter he faced, Ryan Theriot, but he was quickly bailed out by a double play, when Jon Jay's grounder up the middle deflected off Nicasio's glove to shortstop Troy Tulowitzki, who stepped on second and then fired to first to complete the twin killing.
The next time Nicasio came to the mound, he was working with the comfort of a huge lead, as the Rockies scored six in the bottom of the first, tying a season-high for runs in an inning.
"That gave me more confidence," Nicasio said. "I felt comfortable out there, and I went out there and attacked the strike zone, made the hitters swing the bats."
Nicasio, who struck out two and walked a pair, benefitted from a stiff wind blowing in that may have helped to keep a couple deep fly balls in the early innings from leaving the ballpark, and a deft double play started by Tulowitzki in the third -- when the shortstop ranged far to his right and tossed a leaping throw across his body to Eric Young Jr. at second base -- helped kill a Cardinals rally.
Still, Nicasio threw 57 of his 88 pitches for strikes, solid control that Rockies manager Jim Tracy credited to the young right-hander's poise.
"I don't think you can ask much more of a kid coming up and making his Major League debut," Tracy said. "He was fantastic. To go seven innings and handle it in the manner that he did, he just appeared to me to be unfazed by anything. That's another very impressive thing to see."
Nicasio worked mostly with his fastball, which touched 97 mph, while scattering an effective changeup and occasionally mixing in a slider, a pitch Tracy is excited to see the right-hander develop further.
"That's the extra pitch as far as I'm concerned," Tracy said. "If that can become as consistent as the fastball and changeup, then this is, obviously, a very interesting guy."
Whether Nicasio will make another start with the Rockies is yet to be determined. Right-hander Aaron Cook, recovering from a fractured right ring finger, made his final rehab start in Triple-A Colorado Springs on Saturday, and could make his 2011 debut in San Francisco on Friday. If Cook isn't ready, though, Nicasio certainly demonstrated himself capable.
"He was great," catcher Chris Iannetta said. "We really needed a good start, a quality start. He threw a lot of strikes and that's the most important thing. Later on in the game, when he started settling down, he really pitched ... and showed what he was able to do. It was impressive."
Nick Kosmider is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.