It seems the seeds for this departure were sown in late September with the dysfunctional recruitment of Aaron Falzon. Preston was heavily involved in his recruitment, to the point of scheduling a visit. Shortly after Christian ended the recruitment.
http://northwestern.247sports.com/Article/The-end-of-Aaron-Falzon-and-Boston-College-31706056
http://northwestern.247sports.com/Article/The-end-of-Aaron-Falzon-and-Boston-College-31706056