Warren poured in 25 points on 10-of-18 shooting to lead the way for the Wolfpack (22-13), who will travel to Orlando as a No. 12 seed to face the fifth-seeded Saint Louis Billikens in the second round on Thursday.
Ralston Turner chipped in with 17 points and Tyler Lewis controlled the tempo with seven points, eight assists and just one turnover for the victors.
The Musketeers (21-13) totaled seven assists altogether and committed 13 turnovers in failing to earn a victory in the NCAA Tournament for just the second time in their last seven appearances.
Matt Stainbrook led Xavier with 19 points and nine boards.