"It's never been about ability with him," Royals vice president/assistant general manager J.J. Picollo told MLB.com. "It's been just a matter of him staying healthy, and last year was his healthiest year.
"All we wanted for Kyle last year was for him to make it through a whole year, from spring through September, and he accomplished that."
Zimmer, 24, was added to the Royals' 40-man roster last week, thus protecting him from the Rule 5 Draft next month. The Royals project that the No. 3 prospect in their system will start the season at Triple-A Omaha.
"He's a guy who we think can help us at the big league level some time next season," Picollo said. "He has terrific stuff."
The fifth overall pick of the 2012 Draft, Zimmer split time between Class A Lexington (Ky.) and Double-A Northwest Arkansas in 2015. Zimmer dominated at Lexington, posting a 1.13 ERA in nine relief appearances.
At Northwest Arkansas, Zimmer had a 2.81 ERA in 15 appearances, seven of which were starts. The Royals purposely used Zimmer in the bullpen for most of the season to keep his innings down and also to keep him pitching regularly.
Zimmer will be a starter at Omaha.
"We definitely view him as a starter -- and potentially a frontline starter," Picollo said.
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.