I'm a little confused by the premise. If Kyrie were to go down for the season, what would "tanking" mean, exactly?
Would it mean instructing players on the floor to not play to win? The answer to that is always no.
Would it mean instructing Brad Steven to not coach to win? I don't think Stevens has any interest in that and I wouldn't trust a coach that did.
Would it mean trading our valuable vets to get young players and assets? If Kyrie goes down, then the whole team is going to be made up of young players and Al Horford.
So is the question, "If Kyrie goes down, should be trade Al Horford?" I say no.