Here is what I propose with Miller: you give him the start today and the start on Sunday. Unless he significantly improves (say-keep his ERA under 5 for just the next two starts combined, with good stuff as well) then Guzman is in. The Cubs have an off day next Thursday, so the 5th starter spot can be skipped one more time. Guzman would then make his debut May 1st at the Pirates. This does a couple of things-one, it allows Guzman 10 days to get lengthened out for a start-also, it allows the Cubs to keep Miller for a couple more weeks to make sure there's no injury to another starting pitcher, but only giving him 1 more start beyond today in the process. If there hasn't been an injury, Miller gets released or traded before that May 1st date, again as long as he hasn't significantly improved in those 2 starts.