Pomeranz, Colorado's No. 2 prospect, tossed six shutout innings in a 3-1 Cactus League win over the White Sox at Camelback Ranch. The 23-year-old allowed just four hits and struck out two while walking one to improve to 3-0 with a 0.53 ERA over 17 spring innings.

It was his first start in 13 days following a right glute strain, but Pomeranz still managed to cruise through the White Sox lineup.

"It was a little tight, but obviously nothing that was affecting me," Pomeranz told MLB.com. "I was just trying to get ahead of hitters."

The Rockies were already impressed enough by their top pitching prospect this spring to announce Pomeranz as the team's fifth starter on Friday. Because of an off day on April 10, though, Colorado won't require him until April 15, when he'll make his 2012 debut at Coors Field against Arizona.

"We can get his work in on the 10th, and then he'll rejoin the club," Rockies manager Jim Tracy told MLB.com. "He'll leave the club on the 9th to pitch on the 10th and then after he pitches, he'll rejoin the club to do his work with us in preparation for his start."

Pomeranz joined the Colorado system when he was included in last July's deadline-day trade that sent Ubaldo Jimenez to Cleveland. He made a quick impression, pitching 10 scoreless innings for Double-A Tulsa while allowing just two hits and no walks, before receiving a callup to the Majors. Most of his season had been spent with the Class A Advanced Kinston Indians, where he struck out 95 in 77 innings and posted a 1.87 ERA.

Those efforts earned him the No. 24 overall spot on MLB.com's Top 100 Prospect rankings heading into 2012.

After tallying 119 1/3 innings last year in his first professional season, the Rockies will likely skip a number of Pomeranz's starts this year in an effort to prevent wear and tear. Pomeranz said that while he wants to take the mound as much as possible, he understood Colorado's plan for his development.

"I want to pitch, no getting around that," Pomeranz told MLB.com. "But I think they've got a plan to try to limit my innings this year. This is one of the ways for me to be able to pitch if we make the playoffs. I don't want to use them up and feel like they need to set me down when I need to pitch."