Renteria wanted speed at the top of the lineup and went with Emilio Bonifacio and Junior Lake ahead of Castro, who also could lead off in games.
"I think I have some flexibility with the guys," Renteria said.
• Justin Ruggiano did not start Monday against Pirates left-hander Francisco Liriano because of a tender left ankle.
"He had a sore ankle at the end of spring, and we're just trying to make sure we give him one more day and then we have a day off [Tuesday], and he'll be ready to go the following day," Renteria said.
• Top prospects Kris Bryant and Jorge Soler will open the season at Double-A Tennessee. Soler, however, will be slowed because of a sore hamstring. Arodys Vizcaino, who is rehabbing from Tommy John surgery on his right elbow, was assigned to Class A Advanced Daytona to take advantage of the warm weather. Vizcaino will be on a structured program for the first month.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.