I think Gsellman had the potential to be rookie of the year, he may end up one of their best pitchers. He has the best curveball on the team, the most rotations in the majors. He could absolutely dominate.
Wheeler has been starting to show his old stuff. He's he's back, he's proven
to be an Ace. Of course, with his history, there is a risk. A team with a great need for starting pitchers will overpay for him.
If Granderson is playing Center Field, they'll need Largeres to protect leads, pinch run. Even if Conforto plays center, with a lead, Largeres is still the defensive replacement, and Conforto can move to right.
Bruce, playing regularly is the piece to go, keep Gsellman. You can never have enough pitching. Not with Gsellman's potential. He's healthy and young with guts and great stuff.
I think their greatest need is a real defensive catcher, that could handle this young pitching staff, stop the running game, and can handle balls in the dirt. A package could include Bruce, Duda, Wheeler, Travis d'Arnaud. Rivera only looks like a defensive catcher compared to d'Arnaud who is horrible.