Kasdorf did not receive a qualifying offer from the Sabres, Paul Hamilton of WGR Sports Radio 550 reports.
Kasdorf, who signed with Buffalo late in the 2015-16 season, is expected to begin the season as the backup for AHL Rochester this coming season, the Olean Times Herald reports.
The Sabres signed Kasdorf to a two-way contract on Sunday.
Kasdorf made his NHL debut Friday, allowing four goals on 30 shots in a loss to Columbus.
Kasdorf will make his first career NHL start Friday against Columbus, reports John Vogl of The Buffalo News.
Kasdorf (groin) took part in Friday's practice.
Kasdorf suffered a groin injury late into the NCAA season, reports The Buffalo News.
Kasdorf is dealing with an undisclosed injury.
Kasdorf signed an entry-level contract with Buffalo on Monday.