I don't know why you think it's gonna be that ugly (or that much of a beating, to be accurate). Scheyer hasn't done that well against St. John's, and I think this is a different team without the guard depth. St. John's has hung with the Dukies for stretches in the last 2 games (before getting their doors blown off 2 years ago, and a little too late last year).
I think Duke will win. I'm not sure they'll be threatened. But I also don't think they're going to beat the team by 16. That requires a Marquette-level of defensive tenacity that Duke, for some reason, hasn't displayed against St. John's. Hell, consider that Malik Boothe had his highest scoring output from Dec 2008-March 2009 against Duke. The problem wasn't the Red Storm's scoring (for once), it was the Johnnies' defense.
I think they'll call off the dogs early if they're winning, as they have in the past.