An aging heavyweight boxer retires because of injuries, finds a hard time getting a job, and then must step into the circus world of fake wrestling in order to get his manager out of debt.
http://movies.yahoo.com/movie/1800302782/info

Requiem for a Heavyweight (1962)
It's The Set-Up (1949) meets Marty (1955), which (like this story) also had aired previously on television with a different lead actor (in this case, Jack Palance). Directed by Ralph Nelson, written by TV's Rod Serling, and starring Anthony Quinn as the titled heavyweight, this slightly above average boxing drama explores a sometime successful prizefighter's life (he'd been ranked fifth in the world, ten years earlier) at the end of his seventeen year career. The story also includes a quasi-romance between the fallen yet proud (and somewhat punch drunk) fighter and a homely yet optimistic social worker (actually, a government employment agency employee) named Grace Miller (Julie Harris). Jackie Gleason plays Louis 'Mountain' Rivera's (Quinn) longtime manager Maish Rennick, who gets over his head with a loan shark named Ma Greeny (Madame Spivy); Mickey Rooney plays the boxer's more loyal longtime trainer, and friend Army. Stan Adams plays Perelli, a wrestling promoter who offers Rennick (and Rivera) an 'out' with Ma, though it's hardly an ideal opportunity. Muhammad Ali, then Cassius Clay, appears as himself, Rivera's last opponent before retirement; the 'kid' knocks out the old-timer in the seventh round of their bout, at the beginning of the film.
http://www.classicfilmguide.com/index.php?s=other_reviews&item=390

Getting knocked out by Cassius Clay in the seventh round proved to be the end of the line for former heavyweight contender Louis "Mountain" Rivera, Anthony Quinn. After the fight in Mountain's dressing room the fight doctor checking the damage to his left eye tells his manager and trainer Maish and Army, Jackie Gleason and Mickey Rooney, that he can't allow Mountain to fight anymore, the next punch to his head can very well bind or even kill him.

His brains scrambled his fists busted in danger of losing his eyesight 17 years in the fight game is all the battering that Mountain's body could take. And now after 17 years it was time for Mountain to hang up his boxing gloves and go into another line of work, but what kind of work could Mountain do? Unknown to Mountain and his trainer Army his manager Maish had given the Ma Greeny mob the word that his fighter won't last more then 4 rounds with the young and hard hitting Cassius Clay and they place a lot of money on the tip that Maish gave them. Mountain going more then 4 rounds with Clay cost the Greeny mob big and it was up to him to come up with the money by the end of the month or else Maish won't ever have any need for money again. Without Mountain being able to fight anymore the only way Maish can get the money for the Greeny mob is for Mountain to become a professional wrestler and thus making a joke of himself entertaining the public but this time instead of taking punches Mountain will be taking laughs.

Rod Serling's hard hitting screen-play about the fight game and how it chews up and spits out those who are in it like Louis "Mountain" Rivera when it no longer has any use for them. Touching performance by Anthony Quinn as the broken down Mountain who has to humiliate himself by being a clown in the ring as a wrestler after being a proud warrior in the ring as a boxer. Also very moving is Julie Harris as Grace Miller the social worker who does her best to get Mountain a job as a youth consular only to have him lose it by getting drunk celebrating getting it.

As hard hitting as the punches thrown in the ring and as powerful as those boxers in the ring taking them. Mountain makes a fool of himself to save his crooked managers, Maish, hide so he could have the money to pay back the mob that he owes them, but that ended his friendship with Maish. It also educated Maish about being honest and loyal to those who trust and depend on him which is something that he didn't know about up till then. The film ends with Mountain swallowing his pride and accepting what fate had in store for him.
http://www.imdb.com/title/tt0056406/