"We are all devastated for Collin," Villanova head coach Jay Wright said in a statement. "He is the heart and soul of our program. We know we can't replace him. We all just want to step up and play so that we honor him.
"Collin is as mentally tough and resilient as any player we have had here. I know he will get through this and make it a positive for his career."
Gillespie was in the midst of another strong season with the Wildcats, ranking 11th in the Big East in scoring (13.9 points per game) and third in assists (4.6). The senior is one of five finalists for the Bob Cousy Award, which is bestowed annually to the nation's top point guard.
Gillespie was named to last season's All-Big East second team and was a member of Villanova's national championship squad in 2018.
The Wildcats enter Saturday's matchup versus Providence with a 16-4 overall record, including an 11-3 mark in conference play. Villanova clinched the Big East's regular-season crown with their win over Creighton.