Nick Rolovich, former Washington State football coach, plans to sue the university over his termination.
Rolovich was fired on Monday after refusing to comply with the state's vaccine mandate.
An attorney for the former coach told ESPN that Rolovich was denied a religious exemption despite his devout Catholic faith.
Rolovich's attorney claims the university's athletic director, Pat Chun, has planned to fire Rolovich since April.
"Chun's animus towards Coach Rolovich's sincerely held religious beliefs, and Chun's dishonesty at the expense of Coach Rolovich during the past year, is damning and will be thoroughly detailed in litigation," Rolovich's attorney Brian Fahling said in a statement to ESPN.
A two-person panel decided whether religious exemptions would be granted. They did not know the applicant's name or job title, according to ESPN.
Pope Francis, the leader of the Catholic Church, has encouraged Catholics to get the COVID-19 vaccine.
Washington State University has not commented on the threat of the lawsuit.