Logan Paul says the Mayweather family "doesn't give a f**k" if KSI wins their boxing rematch next month ... telling TMZ Sports Floyd's fam is only training him to promote their YouTube channel.
Of course, KSI has been training with some of the top guys in the industry -- including "team advisor" Jeff Mayweather (Floyd's uncle) -- leading up to the Nov. 9 bout at Staples Center, which will stream on DAZN.
24-year-old Paul was training at Wild Card Boxing gym in L.A. on Tuesday ... when he told us his opponent is being used by the legendary family for clout.
"I think the Mayweathers are smart. I think they know if they put KSI's name in their video, they'll get views on their YouTube channel," Logan said.
"Let's be honest. I'm pretty sure Floyd Mayweather or any of the Mayweathers don't give a f**k if he wins or loses the fight ... but you got those views on that YouTube channel!! Way to go!!"
FWIW -- we spoke with KSI earlier this month about his training ... and he's so serious about pursuing a career in the sport, he's already spent $300k of his own dough on training, diet, equipment, etc.
As for Paul ... he's gotten support from Justin Bieber leading up to the fight ... and he hints that the Biebs might be making an appearance!!