It has little to do with panic and more to logic for me. The Cubs should sign Tucker. We all know that they have the money to offer him but Ricketts isn't going to make it that easy so you free up the money by trading Happ and Taillon and you fill LF internally, hope you can get another Rea type to help with the SP depth.
Happ's athletic decline is in pretty apparent effect. He's at that age. I think most organizations would be looking to move a guy like that.