Devin Haney's father Bill Haney, who also serves as his coach, wants Ryan Garcia out of the sport of boxing forever ... telling TMZ Sports he believes the star fighter's flunked drug tests should lead to a lifetime ban.
Bill made the comments to us on Friday ... some 24 hours after Garcia's B-sample came back positive for Ostarine -- a banned substance. His A-sample previously tested positive for the same PED weeks prior. Garcia initially took the tests on April 19, the day before he beat Devin in an instant classic at the Barclays Center in New York.
Bill said the two tests show Garcia is, indeed, a cheater -- and he's now calling for boxing to turn its back on the 25-year-old for good.
"Clearly," Bill said, "there's nothing that you can do with this guy, but get him out of the sport."
"It's a terrible thing," he added. "It's a terrible thing for sports in general. It's a terrible thing for boxing."
For his part, Garcia has denied knowingly taking any performance-enhancing drug -- telling ESPN's Mike Coppinger his pre-fight routine included taking several vitamins ... and "just normal s***."
His legal team stated Garcia has submitted a hair sample for further testing in order to help exonerate him.
Bill, though, clearly ain't buying any of it ... believing Garcia knew exactly what he was doing.
"You see me with my kids," he said, "I don't know what to tell them. The Haneys -- we're fair. We believe in hard work and I feel undermined. For him to sign up to do this and now to make a mockery of the sport -- you know, it's just terrible."
Bill also told us he's not sure his son would take a rematch with Ryan -- even if they could guarantee RG's fight preparations were clean.
The New York State Athletic Commission, meanwhile, said in a statement to ESPN on Thursday it's still in the process of investigating Garcia.
"The Commission strictly prohibits the use of performance enhancing drugs and works vigorously to uphold the integrity of the sport and maintain a level playing field," the Commission said. "Where violations are found, the Commission will take action."