White Sox manager Ozzie Guillen made the announcement after Buehrle gave up two runs, one earned, and five hits in a 4-1 loss to Colorado. He struck out four and walked two.

Monday's game against the Kansas City Royals will be the left-hander's seventh opening-day start, tying him with Billy Pierce for most in franchise history.

Buehrle pitched well against the Rockies but the White Sox committed three more errors to increase their American League-worst total to 43 this spring. Two of Colorado's runs were unearned.

"Defense is my game," Guillen said. "If we don't play good defense, we won't go anywhere. Defense makes good pitching."

Guillen indicated he isn't overly concerned about the problem, saying defense will be easier on big league fields than it is on the hard infields in Arizona. He also said that fielders at times have had a tough time picking the ball up off hitters' bats at Chicago's new spring facility at Camelback Ranch.

Jorge De La Rosa struck out nine in 5 1-3 innings for the Rockies, allowing an unearned run and seven hits.

"I feel much better," he said. "I've started getting my rhythm."

Clint Barmes went 3-for-3 and scored two runs for Colorado. Jeff Baker had two hits and scored twice.

Also on Tuesday, the Rockies reassigned Scott Podsednik to minor league camp, giving rookie outfielder Dexter Fowler a spot on the club.

Notes: Gavin Floyd and John Danks will follow Buehrle in the rotation. Jose Contreras and Bartolo Colon will round out the rotation, Guillen said, though he wasn't certain of the order for the two.