Of course, Cormier lost his heavyweight belt to Stipe after he was knocked out in the 4th round of their main event on Saturday night ... a fight DC was winning before things turned.

Now, Cormier has had a few days to process the loss and issued an emotional statement on social media.

"It’s been a couple of days and I can’t stress the disappointment," Cormier says ... "I am so sorry to all I have let down."

"To my wife and kids I am so sorry you guys had to experience that, I never wanted y’all to see that and the hurt you guys showed breaks my heart everytime I think about it."

"My coaches I am sorry, i appreciate the work and time you’ve spent with me. My fans, thank you guys for all the love and support you have guided me to all these amazing accomplishments."

"Stipe Miocic and his team, congratulations on a tremendous victory, you showed so much heart and grit, you are the definition of Cleveland tough."

As for Cormier's future, the 40-year-old legend says he's still contemplating his fighting career -- and "I will decide what I am gonna do now, and as soon as I decide you will all know right away."

Cormier is one of the all-time greats in the UFC and a surefire Hall of Fame when he does decide to retire ... with signature wins over studs like Anderson Silva, Rumble Johnson, Stipe Miocic, Derrick Lewis, Dan Henderson and more.