Diddy -- Fistfighting Allegations Against Coach Sal Alosi Could Scare Prosecutors

Diddy may have caught a huge break from a chiropractor who just came forward with a stunning allegation against UCLA coach Sal Alosi, claiming Alosi is prone to fistfights, and even had one with a New York Jets superstar.

TMZ Sports has obtained a letter from a female chiropractor sent to Jets brass in 2010 ... raising serious concerns about strength and conditioning coach Alosi. According to the chiropractor, Alosi got into a "fistfight" with Pro Bowl cornerback Darrelle Revis. The doctor added Alosi has a pattern of abusive behavior and the Jets needed to get him under control.

We've learned the chiropractor sent the letter to Diddy's team, and it could be a secret weapon. The D.A. will review the assault case for possible felony prosecution, but if the main victim looks unsympathetic and even violent, it's way less likely they'd go forward. Juries don't like unsympathetic "victims."

The chiropractor also complained Alosi verbally abused and humiliated her, even trying to prohibit her from treating players because he was pissed off over petty issues involving towels and water.

It's unclear how the Jets handled the chiropractor's allegations. Alosi was suspended during the 2010 season for tripping a player during a game, and he resigned from the team at the end of the season.