McMillon cleared waivers and was outrighted to Triple-A Lehigh Valley on Tuesday, Todd Zolecki of MLB.com reports.
The Phillies claimed McMillon (elbow) off waivers from the Marlins on Monday.
The Marlins placed McMillon on the 15-day injured list Thursday with right elbow tightness.
The Marlins recalled McMillon from Triple-A Jacksonville on Friday.
The Marlins claimed McMillon off waivers from the Royals on Friday.
The Royals designated McMillon for assignment Tuesday, Anne Rogers of MLB.com reports.
The Royals optioned McMillon to Triple-A Omaha on Tuesday.
McMillon (forearm) is scheduled to make a relief appearance in Wednesday's Cactus League game against the Mariners, Anne Rogers of MLB.com reports.
McMillon (forearm) is scheduled to throw live batting practice Monday, Anne Rogers of MLB.com reports.
McMillon (forearm) will throw a bullpen session Thursday, Anne Rogers of MLB.com reports.