That would be a huge waste. We have four perfectly acceptable starters in Lester, Arrieta, Hammel, and Hendricks. If you want to add an ace to push Hendricks to the #5 slot and out of the playoff rotation, that's fine. But acquiring two starters would mean that you're using Leake to force Hendricks to the bench. There's no real gain there, except for depth in case of an injury. And since we're just talking about a 5th starter in your scenario, you could probably get a 5th starter a lot cheaper than Mike Leake in terms of prospects after the non-waiver deadline. It doesn't really matter when you acquire them, since you wont have them on the playoff roster anyways.