The old Johnny Manziel is back ... and that's not necessarily a good thing.
TMZ Sports has obtained footage of the Cleveland Browns quarterback raging at a nightclub in Austin, TX on Friday night with a bottle of Dom in his hand ... the second night of a back-to-back bender.
Multiple sources tell us ... Manziel started off his bye week festivities at RIO Rooftop nightclub in Austin on Thursday night ... where witnesses say he partied and boozed with friends all night long.
The next night, he hit up Summit -- where he grabbed champagne and kept the party rolling. Witnesses tell us the bottle wasn't just a prop ... he was boozing there too.
Sources tell us ... Manziel didn't get into any trouble -- but it's concerning considering Johnny entered treatment earlier this year for an undisclosed issue in the wake of some heavy partying.
In fact, when he got out of treatment ... Johnny swore he was a changed man.
By the way, before the bye week ... Johnny told the media he was going to spend his days off relaxing "like everybody else in the locker room."
He also said he was not going to do anything that would "be a distraction to this team or be an embarrassment to the organization."