Scales Tilt Toward Oswalt

These guys say the Sox have been outbid on Edwin Jackson, but Gordon Edes says:

A Red Sox source confirmed Wednesday that the team had not abandoned hopes of signing Oswalt, indicating that the 34-year-old right-hander may have a better chance at a regular turn starting with Boston than with the other two clubs, both of whom appear to have filled their rotations.

Your correspondent is confused. If it's true that the Sox preferred Jackson, how did they not get the deal done?