MLBTR just reported the days off have nothing to do with Halladay.....doesn't say not Lee though.
They'd need to give up Rollins, Howard and Utley to get Halladay anyways.
Yeah, presumably the fourth piece in a trade like that would be one of Drabek, Happ, or Brown, and I doubt one of those guys with Carrasco/Donald/Marson would be enough to get Halladay. I wouldn't think it would be enough for Lee, either, but it does seem kind of strange that Carrasco got the day off when he was scheduled to start.
This also happened last week, though, with Kyle Kendrick, and people speculated he may have been part of a trade, but he was actually just being called up to pitch out of the Phils bullpen.