The move guarantees the Royals a compensation pick between the first and second rounds of the 2008 First-Year Player Draft if Riske signs with another club.
Dean Taylor, Royals vice president-baseball operations, said that Riske is the only one of the Royals' six free agents who has compensation attached to him.
"It used to be that you had to offer arbitration not only to receive your compensation but also to keep your negotiating rights in place," Taylor said. "They got rid of that provision, so now all you're doing is retaining your compensation rights."
The Royals can still negotiate with Riske, who is seeking a multiyear deal. There have been indications in Milwaukee that he's in serious talks with the Brewers.
Because Riske might go elsewhere, the Royals this week signed Japanese right-hander Yasuhiko Yabuta, also a setup reliever.
If a free agent accepts arbitration, he goes on the 40-man roster and is subject to the usual process associated with a salary hearing. However, Taylor said most such cases are settled by negotiation.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.