Mosley won via 6th Rd knock-out, but Mayorga claimed the punch that caught him was a low blow.
The 43-year-old Mosley delivered a powerful left to the Nicaraguan’s body which sent him to the floor.
Mayorga claimed the punch caught him below the belt. The ref thought otherwise and counted him out.
Mosley is well past his prime but was dominated the fight against Mayorga, who bought plenty of bravado, but not much brilliance.