Leave Sanchez alone. Maybe stop letting him go 8 innings when he doesn't need to will help. If you can add a starter I would hope it would be to replace Dickey. And Dickey can spot start to take unnecessary wear and tear off Sanchez. But the starter they get better be someone you can start in the post season otherwise it's pointless.
Seeing what Cashner cost today. That's not going to happen. No way the Jays are paying that much for a rental.