Dave, I had this situation last year with Buda. I had to keep one pitcher designated as not available, even after roster expansion, so just cycle the next game's starter into the ineligible list. A pain, but I didn't see anyway around it. Fortunately, I only had the problem after September call ups.
I concur with Don and Keith. It's a flaw in Strat's system that you can only have 15 pitchers active at any given time. Very irritating. Don's suggestion is the best one that I've heard for dealing with the issue.
I still have it. If someone else wants to look at it that hasn't I'll send it along. I don't remember how much discussion took place about it's merit's, but compared to Strat I didn't like it. I know I have criticized strat in the past, but DM's interface was clunky to me. I don't like being able to see how results are determined. The ratings are more vague. I know from reading message boards that it has a big following. But if put to vote I'd say stick with Strat.