Utah State officials said Berger, a 22-year-old junior forward from Medford, Ore., collapsed during practice Tuesday. Training staff administered cardiopulmonary resuscitation and used a defibrillator on Berger before an ambulance arrived and took him to a hospital.
A university news release said Berger was still listed in crucial condition Wednesday.
Berger averaged 7.6 points and 3.6 rebounds over five games this season.
Wednesday's game between Utah State and Brigham Young in Provo, Utah, was postponed. Officials said it would be rescheduled. Utah State's next scheduled game is at home Saturday against Western Oregon.