Dempster has almost 1000 innings as a starter with a 5 ERA and a 4.7 BB/9 that didn't really improve when he became a reliever. The conceptual idea of "use Marshall as a trading chip and replace the hole in the rotation from within" isn't a bad one, but I'd put Dempster behind Marmol, Gallagher, Prior, Hart, and maybe even Wood on the list of people used to fill that hole.