The former NL Rookie of the Year was a non-roster invitee to spring training but missed the final couple of days with a strained right groin.
Nomo, 39, who has not pitched in the majors since the 2005 season with Tampa Bay, joined the team Saturday for work in the bullpen.
Nomo was 1-0 with a 4.80 ERA in 15 innings this spring. His comeback bid drew considerable attention as a crowd of Japanese reporters followed the Royals in spring training.
He was sent back to the spring training facility in Arizona for physical therapy after injuring his right groin muscle last week.