The Golden Eagles (24-8) will play the winner of the UTEP-Houston game in Friday’s semifinals.
Watson and Davis had five assists apiece, and both went 7 for 11 from the field with Davis making four 3-pointers and Watson three. Davis was coming off of back-to-back 30-point games against Marshall and UCF.
Southern Miss shot 53 percent, led 40-26 at halftime and never saw its second-half lead dip below seven points.
Rod Rucker scored 20 points to lead the Blazers (16-17), the No. 7 seed. Preston Purifoy added 10 points. UAB beat SMU 53-52 in the first round on Wednesday.