Revealing mistake: At the very beginning of the movie when Billy is getting his hands wrapped as Eli is taping his right glove, part of the H in his fighter tattoo has been rubbed off from when his arm was resting on the chair while they wrapped his hands. (00:02:40)
Continuity mistake: When Billy's wife Maureen is lying on the ground dying, in one shot her teeth and lips are covered in blood, then in the next shot all the blood in and around her mouth is gone. (00:28:20)
Continuity mistake: After the last fight at the locker room, Billy is hugging his daughter and has his right hand on Leila's head but in the next shot the hand moves away.
Continuity mistake: Before the 11th round Billy is seated on his corner and has some drops of blood on his chest but in the next shot the blood is gone.
Continuity mistake: After the 5th round the amount of blood on Billy's left eye changes between shots while he is on the corner.
Continuity mistake: When Billy and his daughter are at Moreen's grave the sun changes between shots.