I don't know why so many presume West will automatically be the primary Kanter defender. It's proven that he can't defend him in the post or keep him off the offensive glass. He's obviously not the answer and Marjanovic is probably a last resort.
This is the series where Duncan will be most needed and as such, I expect him to be the primary Kanter defender. He'll still come out at the under 6 timeout, only in this series, he'll re-enter for Aldridge 3-4 minutes later and come back out again when Kanter does (probably around mid quarter).