Lurker here,
I want to propose a TV movie-like scenario of what led to Slice's departure...
Once upon a time, Chris calls up his good friend Barry and says, "come with me. I'm going to be the new head coach at St. John's. We'll recruit together, coach together, and make a tournament team. It'll be great. Just like old times!"
But then, Chris hired Mitch as his special assistant. Barry loses Chris' ear to Mitch because Mitch turns out to be a very capable. Chris and Mitch work very well together creating player development programs. These programs are very persuasive in recruiting players, but this wasn't Slice's strong suit. Slice sulks and further loses Chris' ear. And then Matt is locking down players, where Slice isn't. Barry sulks some more. And then either side couldn't take it anymore.
And here we are.
This may be pure fiction, but this could very well have happened.