Afterward, Shields had a brief session with Royals pitching coach Dave Eiland to review his work.
"Every time you're back on the mound and start throwing to hitters again, you've got to kind of remember what you worked on last year and that kind of stuff," Shields said. "It's just a process of getting your mechanics going and getting everything in line."
Shields served up pitches to a couple of Minor Leaguers as well as catcher Frank Pena.
"I think I had one homer hit off me today," Shields said. "When you're telling 'em what's coming, it's a little easier to hit, I guess."
It was Pena who banged the home run, but he noted that Shields' command was excellent and his fastball and changeup were working well.
"His stuff was electric," Pena said.
Although the Phoenix area temperature hit a record 88 degrees on Monday, the Tuesday morning workout was in a pleasant 74 degrees.
"Everything went really well," manager Ned Yost said. "Everybody's getting good work in, everybody's feeling good."
Most of the infielders and outfielders are already in camp and were taking batting practice on Tuesday. Their official reporting date is Wednesday, with the first full-squad workout on Thursday.
Shortstop Alcides Escobar, the only regular who has not yet turned up, is expected on Wednesday, Yost said.
Yost has two intrasquad games scheduled for Feb. 25 and 26. The first game is Feb. 27 against the Rangers.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.