The 6-foot-4 guard averaged 8.7 points last season in 26 minutes per game but decided to play elsewhere shortly after the coaching change in which Richard Pitino replaced Tubby Smith.
"It came down to the fact that Coach [Randy] Bennett has been able to develop guards and also that they have playing time available," Coleman told ESPN.com. "When Coach Smith left, I decided I wanted to go somewhere that I could expand my game."
Coleman will sit out this season and have two years left with Bennett and the Gaels. He also visited Creighton and drew interest from Gonzaga, Florida State and Oregon.
Saint Mary's, which was 28-7 this past season, graduated star guard Matthew Dellavedova and also lost signee Cullen Neal, who was released from his letter of intent in order to play for his father, Craig, at New Mexico.