Sage Northcutt Is 100% Down to Fight Logan Paul, 'Could Be Massive!'

If Logan Paul REALLY wants an MMA fight -- Sage Northcutt tells TMZ Sports he's READY!!!

Remember, before his big boxing match with KSI, Logan said his dream is to fight in the UFC.

Well, Sage has 8 fights in the UFC under his belt -- and told us, if Logan is serious ... bring it on!

"I think my fans would love watching that," 22-year-old Northcutt said on the "TMZ Sports" TV show (airs weeknights on FS1).

"It could be massive."

Sage says he's impressed with Logan's high school wrestling accomplishments (he placed in the Ohio state tournament, one of the most respected state tourneys in the country).

He also watched Logan's boxing match and thinks the dude has real talent.

"I would like to see myself fight him ... I think it would be a good match-up."

And, if Logan isn't down for a true mixed martial arts fight -- Sage says he's down for a traditional boxing match, too.

"This actually could be really cool."