"He does have a feel for what he's doing," manager Clint Hurdle said. "He's being challenged at this level, and we wanted to get him out there in a starting opportunity. I saw a kid with good mound presence that can sink the ball."

Chacin led the minor leagues with 18 wins last year, going 10-1 with a 1.86 ERA in 16 starts for low Class A Asheville, then 8-2 with a 2.31 ERA in 12 starts after moving up to high Class A Modesto. His combined 2.03 ERA ranked sixth in the minors, and his total of 177 2/3 innings ranked third.

"He's not afraid to throw his pitches in the strike zone," Rockies pitching coach Bob Apodaca said. "There's no fear of contact. He has a very good grasp of the off-speed pitch at a young age."

Chacin, a native of Venezuela, has a superb changeup, which nicely complements his 91-93 mph fastball. His third pitch is a curveball, which he's in the process of refining. Chacin has a clean, repeatable delivery, very good fastball command and last year averaged 2.1 walks per nine innings.

"I won't say he's unique, but he's beyond his years," Apodaca said.

As for Cook and his game against the minor-leaguers, he threw 78 pitches in six innings and allowed four hits and four runs, three earned. Cook took advantage of the situation and threw mainly curves and changeups, calling it "a luxury" to be able to work extensively on those pitches.