What I glean from the reading I've done is that Capers/MM like the talent the rookie CB's have well enough, but don't think they have a big-picture understanding of what the defensive plan is designed to do, and so can't be trusted not to bust a coverage and give up the easy TD.
I suppose there's no room for error, so I understand playing it safe with the safeties playing corner, but I'd be tempted to go with the talent over the understanding, and hope the understanding catches up - fast.