my great missunderstanding
As I watched the film I was somewhat bemused durring the beginning and I began to believe that the young boxer Was in fact the young version of the old boxer. This missunderstanidng made total sense to me throughout the film...the fury of his past made him a slave to his anger, regret and vengence which made him the broken man he was an old man.
I thought the great loss the old man suffered long ago would be the lose (though he didn't lose) the young boxer would suffer in the last fight.
The fight in the end I thought was a metaphor for the lesson the old boxer finally learned which made him relinquish his hate and vengence of the world; that there is never anybody else - there is just you, fighting a shadow forever, until you se one day that you were fighting yourself all along... and never anyone else. There is just you and yourself, nothing more.