I'd let Harvey drift away. No offer of an extension. Focus instead on deGrom, Syndergaard, Matz, Wheeler, Gsellman, and Lugo. And Montero too, I guess. There's no guarantee that you'll find four or five solid starters among them, but Harvey seems the least likely to succeed. I really doubt that he'll ever be what he was. Maybe he can reinvent himself some day as a crafty old lefty, but in order to do that, he'd have to start by learning to pitch left-handed.