I wouldn't do it. You've got two of the better catchers in the league. Somebody is going to place more stock in Weiters down the line and could offer you more than Fowler.
At least shop him first and see what he's worth to other teams.
Depending on rosters, catchers are hard to come by, ya can always trade Wieters later.
I known Fowler for years & he will never be keeper material or past a top 70 player in my opinion.
I think you can do better for Wieters.
Don't do it. Catcher is a premium position and Weiters has good power. Everyone has been waiting for Fowler to break out for years now and although he had a better season (#'s improving all around), Rockie players can't hit outside of the Mile High city.
