"This much is known: Rockies right-hander Aaron Cook will not start Saturday as previously scheduled. This much is certain: Cook no longer has a lock on a rotation spot.

Inflammation in his right shoulder has left Cook performing strengthening exercises and playing light catch. Manager Jim Tracy said he would like Cook to throw two side sessions and live batting practice before making his Cactus League debut. That means it will be next week, at the earliest.

"Of course it's frustrating. I want to be out there, but I am not a doctor," Cook said. "I have to listen to the advice of the training staff."

Cook began experiencing shoulder stiffness after his first side session in camp. The winningest pitcher in Rockies history is coming off his most disappointing season. He went 6-8 with a 5.08 ERA.

"There was no pain or anything in the winter leading up to this. It's probably just from throwing 2 billion pitches in my life. I know that sounds sarcastic, but you just never know sometimes why this happens," Cook said.

The Rockies created competition by acquiring Felipe Paulino. Esmil Rogers also enjoyed the best winter of any pitcher in the Rockies' Dominican program, according to Rolando Fernandez, Colorado's director of Latin operations.

Rogers will start in Cook's place Saturday against the Royals, and is scheduled to throw three innings."