Ben Affleck appeared on the series premiere of Bill Simmons' "Any Given Wednesday" tonight and it was extremely bizarre ... to say the least.

A red-faced Affleck ranted about "Deflategate" on the HBO show and even though we can't say for sure what was up with him ... social media was quick to call Affleck out for his slurred speech and angry tone.

Sources close to Affleck tell us he's stone cold sober. As for the slurring ... Ben's just passionate about Tom Brady. We're told him and Simmons got into a heated, loud "Deflategate" debate before the cameras started rolling. So when the show started, Ben was already fired up.

Watch the clip below and decide for yourself.

(WARNING: EXPLICIT LANGUAGE)