Duffy, 27, is eligible for arbitration this offseason after making $4,225,000 in 2016.
Royals general manager Dayton Moore said by phone Friday that he would not comment on potential discussions regarding a Duffy extension.
"But it has always been our intention to keep our young talent when possible," Moore said.
Duffy, who is eligible to be a free agent after next season, is coming off a career year. He set career highs with 179 2/3 innings and 188 strikeouts while going 12-3 with a 3.51 ERA and a 1.14 WHIP.
Duffy emerged as the team's ace this season after starting the year in the bullpen. He quite likely will be the Royals' Opening Day starter in 2017.
Duffy said he was not aware of any contract negotiations going on, and he admitted to being somewhat "out of the loop" on such matters. He is represented by the ACES agency.
"I pretty much let my agents take care of that stuff," said Duffy, who was doing some charity work on Thursday at the Kansas City Pet Project.
But Duffy made it clear where his loyalties stood.
"I want to stay with the Royals long term," Duffy said. "One-hundred percent. For sure. You can quote me on that."
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.