Chris Wright hauled down 11 rebounds and scored nine points as the Flyers (21-12) used a stifling defense to hold Illinois State to a paltry 33.3 first-half field goal shooting percentage, allowing Dayton to post a 30-19 halftime lead.
Osiris Eldridge led the sixth-seeded Redbirds (22-11) with 12 points despite shooting just 4-of-15 from the field, and collected five caroms in the loss.
With the win, Dayton advances to play No. 2 seed Cincinnati in the second round.
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