Cruz, ESPN insider Kiley McDaniel's No. 13-ranked prospect, was optioned to Triple-A Indianapolis on Tuesday.
A towering, 6-foot-7 shortstop, Cruz put together a solid spring training, going 5-for-15 with two home runs in Grapefruit League play, but manager Derek Shelton said the team believes Cruz needs a little more experience before being called up for good. Cruz hit a home run in October during a brief big league cameo.
"It was a development decision," Shelton said. "There's still room for development and still things that we feel he can maximize on."
Cruz, 23, played 63 games at Double-A Altoona and six with Indianapolis before being called up to the majors at the end of last season. Shelton pointed to that lack of experience as one of the reasons to send Cruz down.
"We feel that he's going to have a major impact on the Pirates," Shelton said. "But right now, we feel like there's things for him to do moving forward [in Indianapolis] that's going to help us win games."
The Associated Press contributed to this report.