Saints could get to $14.61 million under the cap without restructuring Derek Carr, after Saints salary cap potentially increases by $5M

Luckily, we will get that answer with what they decide to do with Carr.
I don't think letting go of Carr would automatically equal a rebuild. It wasn't a rebuild when they got him, so they could move on from him without it being a rebuild. Then again, rebuild is a very subjective term that looks different to different people.