Forgive me if this has been posted elsewhere and I missed it...
but in the event that the Reds don't show much improvement by mid-May, it certainly seems possible that Castellini will consider replacing Narron.
The biggest name that comes to my mind -- espeically if the Reds want someone to come in and shake things up, but also someone with some name value -- is Joe Girardi. Granted, he has only one year of experience, but he won with a small payroll, overachieved, and was regarded as a guy who will get in players faces. At the moment he's working for the Yankees TV network.
It's pretty rare to see a mid-season replacement manager get a team turned around that season for a playoff run -- in our case, Davey Johnson needed a year to get things turned around when he came on board in '93 -- but it's not unprecedented either. (Jack McKeon did it with FL in '03, and won the world series.)
Curious to hear other names that people think would get looked at...