Callaspo has been out since June 28 when he was placed on the disabled list for an unspecified medical condition. That came after he was arrested in the early morning hours of June 27 on suspicion of driving under the influence.
"He's back working out with the team," general manager Dayton Moore said. "We expect him to spend some time working out and conditioning his body. We'll send him out on rehab when the first phase of his conditioning is completed."
Callaspo will get an injury rehabilitation assignment in the Minor League system when he's ready.
Meantime, relief pitcher Yasuhiko Yabuta is expected to remain in the Royals' organization after being designated for assignment on Saturday.
Yabuta, signed for two years at $6 million last winter, had a 1-3 record and 5.46 ERA in 26 games when the Royals optioned him to Triple-A Omaha on June 25.
He's been up-and-down with Omaha with a 2-3 record, one save and a 5.40 ERA in 12 games.
"He's doing OK," Moore said. "We still like him."
The Royals have 10 days to put Yabuta on waivers, trade him or release him. When that period is over, he's expected to accept an assignment to Omaha.
"We'll have him in the organization for the remainder of the guaranteed portion of his contract through next year," Moore said.
Yabuta was designated for assignment to clear room on the 40-man roster for infielder Jason Smith, whose contract was purchased after Mark Grudzielanek went on the disabled list.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.