Former world champion and current fight promoter Oscar de la Hoya has entered a treatment facility and will miss Saturday's blockbuster Floyd Mayweather v Saul "Canelo" Alvarez bout.
De la Hoya's Golden Boy Promotions played a key role in setting up the bout in Las Vegas, which is set to be one of the richest in history.
Mayweather, 44-0 with 26 knockouts, will be gunning for Alvarez's World Boxing Council and World Boxing Association super welterweight titles, while Mexico's Alvarez will be trying to improve his own 42-0 unbeaten record against the American great.
"Canelo Alvarez and I have big fights coming up this weekend. His is the ring and mine in treatment," de la Hoya said in a statement.
"I will not be at the fight to cheer Canelo to victory since I have voluntarily admitted myself into a treatment facility.
"I explained this to Canelo and he understood that my health and longterm recovery from my disease must come first."
De la Hoya first admitted two years ago that he was an alcoholic and drug user and had been in rehab but did not specify why he was being treated this time.
The 40-year-old won Olympic gold for the United States in 1992 and won world titles in six weight classes as a professional before retiring from the ring shortly after he was beaten by Manny Pacquiao in December of 2008.