http://news.nationalpost.com/2015/01/25/toronto-raptors-still-trying-to-find-best-fit-for-jonas-valanciunas/
This article tells you why Casey doesn't have JV out there in crunch time. Casey likes his bigs to be be able to help and hedge on the PnR but with JV he isn't mobile enough to do that, so thats why he doesn't "trust" him.