Sage Northcutt tipped the scale at 170 lbs. on Friday ... but he'll be a helluva lot heavier in the future -- as in, the size of a 206+ lb. heavyweight -- 'cause that's where Super Sage says he'll eventually fight.
TMZ Sports talked to the UFC star before his co-main event fight against Zak Ottow at Saturday's UFC Fight Night 133 -- a fight in the 170 lb. welterweight division.
That's a step up for the 22-year-old -- who's been fightin' at 155 lbs. -- but it ain't the final destination.
"Personally I think I might end up fighting heavyweight in the future," Sage tell us.
"I can just see myself keep growing. I'll be 24, 25, growing 2, 3, 4 more inches, and putting on a lot of muscle. I can absolutely see it."
And hey, with Nick Diaz also talking about taking heavyweight fights ... things could get interesting.