As you might recall, Millwood signed a minor-league contract with the Yankees earlier this spring, with the option to become a free agent if the Yankees didn't bring him to the majors by the 1st of May. With both Bartolo Colon and Freddy Garcia pitching well, the Yankees had no need for Millwood and he did free himself from the pinstriped shackles.
Millwood started only three games in the Yankees' system, and was absolutely hammered in his two Triple-A starts, giving up three home runs in nine innings. So this deal speaks more to the Red Sox's desperation -- with Daisuke Matsuzaka and John Lackey on the Disabled List, indefinitely -- than to Millwood's talents at this point in his career. He will presumably join the Pawtucket rotation and try to out-pitch fellow senior citizen Brandon Duckworth.