Francis dealt with injuries but was coming off an impressive 2007 season (17-9 215 IP 114 ERA+). Blanton was ineffective but has a track record of an innings eating middle of the rotation starter (he's also starting game four of the World Series).
Zack holds his own compared to his draftmates and while it may have taken him longer to get established he's there with them right now and most likely will get better. Hamels is the only one I would trade straight up for him, Kazmir has electric stuff but is a bit too fragile for my taste. So this convinces me now more than ever that Greinke should not be traded unless he flat out rejects any extension talk - and even then only if Moore gets an overwhelming offer.