The fact of the matter is, because of the expectations around guys repeating their minor league level, Caissie's stock was probably (mildly) down this year until some point in the last week or two. He *needed* to have a stretch like this to justify keeping his status as a top ~50 prospect IMO.
Caissie's certainly too good to be used on a rental, but I feel comfortable moving him this month. For instance I'd gladly include Caissie in deals for Griffin Jax or Edward Cabrera. I'd reluctantly include him in a Keller/Bednar deal. And I'm on the fence on a Kris Bubic deal.
Ideally we would know what's going to happen with Tucker before we moved Caissie, but with Alcantara, Long, and Ballesteros in hand it's not a massive consideration IMO.