Jon Jones just received some well-wishes from a very unlikely place ... Daniel Cormier's trainer -- who tells TMZ Sports they're rooting for the UFC champ to beat his drug problem ... despite the bad blood.
FYI -- Jones and Cormier HATE EACH OTHER'S GUTS ... and trashed each other like crazy before and after their fight at UFC 182 this past weekend.
But Cormier's trainer Javier Mendez tells us ... when it comes to Jones' battle with drugs, it's one fight they actually want him to win.
"The most important thing is his health," Mendez tells us ... "We hope that he gets better soon and gets the help that’s needed."
As we previously reported, Jones checked into a drug treatment facility after a test revealed traces of cocaine.