TMZ Sports spoke with Audie Attar after the dramatic weigh-in Friday morning when Lee initially weighed in 1 pound over the 155 lb limit ... putting the fight in jeopardy.

Officials gave Lee an hour to lose the extra pound -- and if he didn't, Tony could have opted out of the fight.

But Attar says Ferg wasn't about to let Lee off the hook that easy -- "If Kevin wanted (to) move forward, Tony definitely did."

Ultimately, Lee made weight ... and the fight is on.

Of course, this ain’t the first time Tony’s had an opponent with weight issues -- his UFC 209 fight was scrapped after Khabib Nurmagomedov had medical complications during his weight cut.

FYI, the winner of Ferguson vs. Lee could be the next in line to face undisputed lightweight champ Conor McGregor ... especially with Nate Diaz demanding BIG money for a trilogy fight.