Butler and Xavier are leaving the Atlantic 10. Creighton departs the Missouri Valley Conference.
The Billikens wasted a chance to win a share of a conference title for the first time since 1970-71 in the Missouri Valley.
Brian Conklin had 14 points for Saint Louis, which certainly will get its first NCAA bid since Rick Majerus became coach in 2007-08. The Billikens were last in the tournament in 2000.
Xavier led 39-29 at halftime but shot just 28 percent afterward. That helped St. Louis take control with a 24-2 run over an 8:34 second-half stretch.
Billikens fall 76-68