Marra, a starter in nine games this season, sprained his right ankle in practice Tuesday and could be out 2-4 weeks.
One of Louisville's top three-point weapons, Marra is averaging 9.3 points, 2.8 rebounds and 2.7 assists this season. He has scored in double digits in seven of 10 games, and had made 20 three's in the first ten games this season.
Louisville also will be without Justice, the primary reserve for starting point guard Peyton Siva. Justice suffered a concussion Saturday against Gardner-Webb. He averages 4.7 points and 1.9 rebounds this season.
With Justice sidelined, Louisville likely will turn to another freshman, Russ Smith, to give Siva a breather against the Hilltoppers.
Western Kentucky starts a true freshman at point guard. Brandon Peters, a 6-1 guard, averages 6.5 points and 2.5 rebounds.
"They're very quick on the perimeter, the offensive rebound well and they play for steals," Rick Pitino said of the Hilltoppers. "It's going to best a test for us on the road before we go into the Big East."
Western Kentucky has won two of their last three games, but lost their last game against Murray State, 69-60. The Hilltoppers are led by forwards Steffphon Pettigrew and Sergio Kerusch, who average 25.2 points, and 12.1 rebounds collectively.
The game is set for 8 p.m., and will be televised on Fox College Sports and in Louisville on WKYI.