Barstool Sports president Dave Portnoy is coming to terms with the fact Tom Brady is no longer a New England Patriot ... and he's convinced this could be the end of the world as we know it.
Remember, El Pres told TMZ Sports less than a month ago ... "Anybody who says (Brady's) going anywhere is an idiot!!" ... and obviously, TB12's leaving.
We reconnected with Portnoy in wake of the news on Tuesday ... and despite the devastating news, the guy is actually taking it well.