I listened to the interview, and DD provided the caveat that JBJ would have to hit to be the full time CF. It wasn't a given that the OF alignment would be Castillo/JBJ/Betts, but that DD felt that JBJs defensive ability warranted an opportunity to play CF full time IF he could hold up offensively. I like JBJ as much as the next guy, and I fully admit that JBJ is the better defensive player, has a better arm, etc. than either Castillo or Betts. That being said, I believe there is also value to having a franchise caliber player (like Betts) stay in one spot, especially because he certainly acquitted himself well in CF in 2015, and was comfortable there. JBJ may well be the Sox CF for the next 5 years or so, but I don't think anyone views him as a franchise player. I'd love to see JBJ hit like he did in Pawtucket, admitting that the August rush was a small sample. If JBJ can hit .270/.350/.450, he's a major asset to the team. Betts has already shown extended levels of performance at that level or higher, and is 3 years younger than JBJ. For my money, as much as I love JBJs defense, I want Betts left alone in CF, with Bradley platooning in RF with Castillo and LF manned by someone else probably not yet on the roster. JBJ can be a late inning defensive replacement on an OF corner when he's not starting against LHP, but that's how I'd use him until he proves he can sustain a prolonged level of offensive productivity-which I think he could. When he actually DOES, then he'll play full time, but in RF, not in CF.
I fully acknowledge that this is a minority opinion, but I really do think there is value in having the face of your franchise (which Betts is going to be when Ortiz retires, though Pedey is the elder statesmen and still a very respected player) stay in a stable, important position and leaving him there. He's a good CF, and Bradley can be a great RF next to him. Just one man's opinion.