Royals general manager Dayton Moore did not immediately return a call on Saturday night, but it was known that a Royals scout was in attendance at the Reds-Rockies game in which Cueto pitched. Cueto threw eight shutout innings in Cincinnati's 5-2 victory.
Reds pitcher Michael Lorenzen told Cueto before the game he was being traded, according to Mark Sheldon of MLB.com.
Earlier this week, Moore told MLB.com that he did not feel a deal before the non-waiver Trade Deadline on July 31 was a must, but that if the right deal came up the Royals would do all they can to execute it.
If the FOX Sports report is accurate, and the deal fell apart because of a medical issue, that could allude to injuries sustained in the past two years to top pitching prospects Kyle Zimmer and Sean Manaea, both of whom are actively pitching in the Minors, however.
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.