We've talked about this a lot recently, so I won't belabor it here, except to this that this isn't what I would do. The offseason is young, though, and there's really nothing to do except give the front office some slack until another shoe drops. I don't think the Pirates will go into Spring Training with the rotation options they currently have.
Speaking of which, one Dodgers blogger is currently reporting that the Dodgers and Bucs are working on a trade of Chris Capuano for Joel Hanrahan. Capuano has been decent and durable for two straight years, but I hate the idea of giving up an asset like Hanrahan for a veteran who's merely competent and who will be a free agent after 2013. The only crucial advantage Capuano has over Karstens is that Capuano has held up the past two years, so dumping Karstens and trading Hanrahan for Capuano would amount to little more than a salary dump. Again, the Pirates may deserve the benefit of the doubt on this. I really don't think they would trade Hanrahan for Capuano one-for-one.
UPDATE: The Pirates have designated Karstens for assignment.