Zion Williamson & Duke Fuel Up On Fancy Steaks Before Virginia Tech Game

How are Zion Williamson and the Duke Blue Devils getting ready for the biggest game of their season??

FILET MIGNON, BABY!!!!

TMZ Sports has learned Duke hoops hit up Mastro's Steakhouse in Washington, D.C. on Thursday night to fuel up on delicious meats before their monster tilt with Virginia Tech on Friday.

We're told the entire squad was there -- from Coach K and his wife to Zion to even the ball boys -- and they grubbed on steaks ... and, of course, the legendary butter cake!!!

We're told, in all, there were about 40 people in the Blue Devil party -- and even Barack Obama's best buddy, Reggie Love, showed up!!

Unclear who picked up the tab for the meal -- but it surely wasn't cheap ... Mastro's is known as one of the finest restaurants in the country, costin' about $50 per steak.