"Some of them were in my lungs," Gee said. "I had one large one in the subclavian vein, and that was taken out. The lung ones are treated with blood thinners, and they just go away."
Doctors in Detroit became suspicious that the clots were being caused by thoracic outlet syndrome. Gee eventually flew to St. Louis and was examined by Dr. Robert Thompson, a TOC specialist who confirmed that Gee had symptoms.
Gee thus will have TOC surgery on Oct. 11. Royals pitchers Chris Young and Luke Hochevar also have had TOC surgery.
"[Dr. Thompson] made me feel better about the whole situation," Gee said. "He thinks I'll be fine."
Gee, a pending free agent, said he could be ready for Spring Training.
"[Dr. Thompson] thinks so," Gee said. "But I talked to the trainers and they said being ready for Spring Training might be a little aggressive. You never know. Obviously we're going to take our time and get it right."
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.