EXCLUSIVE

Every so often a man finds himself at a crossroads, where the choice he makes will forever alter the course of his life. Or, in Matt Damon's case -- he has 2 awesome choices and really can't lose.

Here's the deal -- Damon's a huge UFC fan and, on Saturday night in Las Vegas, Conor McGregor will take on Khabib Nurmagomedov for the lightweight championship at UFC 229. It's a highly-anticipated fight and will be a huge draw, and Matt's got a seat Octagon-side for the action.

But as we all know ... Damon also KILLED as Brett Kavanaugh on last weekend's "Saturday Night Live." Almost everyone wants and expects Matt to play the role again this weekend ... especially with the full Senate vote on Kavanaugh expected on Saturday.

Apologies to Lorne Michaels ... but sources close to Damon tell us he's decided to go to Vegas for the fight.

We're told the lure of McGregor's return to UFC outweighed a reprise as Kavanaugh.