The move "completely blindsided" both Darner and his coaching staff, according to Stadium's Jeff Goodman.
Darner had been with the Phoenix since 2015, posting a 92-80 overall record. During his first season, he led the school to its first NCAA Tournament appearance in 20 years.
The 49-year-old had triggered an automatic one-year extension this past season by finishing within the Horizon League's top four, sources told ESPN's Jeff Borzello. That reportedly extended his contract through the 2025-26 campaign.