Seems to me, most modern closers fall into one of three catagories. The kind that miss bats until the day they hang up the glove (rare these days, but Billy Wagner for example) the kind that start to lose the ability to miss bats but figure out how to get outs other ways (Trevor Hoffman, Jon Papelbon) and the guys who start to lose the ability to miss bats and ride out the rest of their career on a series of rebounds and busts (Francisco Cordero, Jose Valverde, Troy Percival). Perk looks almost certainly to be in one of the later two catagories. As he tends to have pretty good control, one would hope that he can learn to pitch to his limitations, but there is a long history of pitchers flaming out once their velocity leaves them.