The former All-Pro receiver was high on Dallas before kickoff ... saying he was "feeling EXTREMELY EXTREMELY great" about America's Team and claiming a $10,000 payday was on the line.

But things quickly went south for Dez ... as Green Bay came out strong with a 27-0 lead and never looked back.

That's when Dez -- who played for the Cowboys from 2010-2017 -- started to unravel.

"Idk wtf going on but we really need straighten up," Dez said ... still holding out hope for a comeback. He later bashed Cowboys staffers ... adding, "Playing (sic) calling trash as f*** right now."

As Dallas started to pick things up in the second half, Dez remained optimistic ... saying, "I still believe in us… game not over" and "If we can score one more time before the 3rd up. I like our chances."

In fact, he claimed he was about to make a live bet on Dallas completing the comeback ... but shortly after, he accepted the inevitable outcome.

"Yea this one might be over."

Bryant gave his two cents on the future of the Cowboys ... saying the organization should fire defensive coordinator Dan Quinn.

"Quinn was ready to leave Dallas," Dez posted. "Fire his ass Jerry and give him his wish."

But it doesn't sound like Bryant is solely putting the blame on Quinn ... as he said the current roster was "too damn talented for this."

Green Bay ended up taking the 48-32 victory ... securing a spot in the Divisional Round, where they'll face the San Francisco 49ers. It was certainly not what people were expecting ... as Dallas was believed to be a Super Bowl contender, and the Packers snuck into the postseason with a 10-8 record.

Gotta give Dez credit for being 100% real throughout his heartbreak ... and he got over his troubles with the help of an adult beverage.