As a result of several moves the Rockies made Wednesday, Nicasio will start Thursday's opener of a four-game series at home against the Dodgers.
To make the start possible for Nicasio (1-1, 2.08 ERA), who beat the Cardinals and lost to the Giants in his outings, the Rockies on Wednesday:
Optioned right-hander Greg Reynolds to Triple-A Colorado Springs to work as a starter -- a move that opened a spot so right-hander Aaron Cook could be activated from the 60-day disabled list to start Wednesday against the Padres.
Announced that right-hander Clayton Mortensen, who threw six scoreless innings in the Rockies' 3-0 victory over the Padres on Monday, will pitch out of the bullpen.
Announced that righty Jhoulys Chacin would have an extra day's rest and start Friday, and righty Jason Hammel also would have an extra day's rest and start Saturday. Right-hander Ubaldo Jimenez will start Sunday's finale against the Dodgers.
Mortensen and Reynolds will offer protection in case Nicasio struggles and needs to return to the Minors. But the Rockies want to see how far Nicasio can go after his early impressive outings.
"He throws 95, 96 mph," Rockies manager Jim Tracy said. "He has a slider that has to continue developing. He has been hurt with the pitch a couple of times in his outing. But he is a strike-throwing machine with downward plane that drives the ball down, and he's a very competitive kid with a lot of poise.
"When you're throwing low strikes at 95 or 96, that's hard to hit."
Mortensen (2-3, 3.20 ERA in nine games, six starts) said instead of mourning being taken out of the rotation, he immediately snapped into bullpen mode when informed of the decision.
"It's a slightly different mindset, but it's a mindset that I'm familiar with; it's something nice to get into," Mortensen said. "It'll be kind of cool. We'll see how it works out. Whatever they need, I'll be ready for it."
Reynolds (2-0, 4.08 ERA in five games, two starts), a starter by trade who had pitched as a starter and a reliever during two callups, had been idle since May 30.
A former top Draft pick, Reynolds is happy to have established himself as dependable option. Reynolds said he isn't sure when his next start in Colorado Springs will be.
"It's where I'm at in my career," Reynolds said. "I'll probably be up and down a bunch, and whenever they need someone, I'll be ready. In the meantime, I'll go down there and continue the progress I'm on, continue the way I've been throwing.
"With what I've done, I haven't given them a reason to look somewhere else. That's definitely a good thing."