Cook returns from a right forearm strain, adding another late-inning arm to the Athletics' already formidable bullpen. Manager Bob Melvin said Tuesday before facing the New York Yankees that he will ease Cook back into the mix.
Out since May 8, Cook was 0-1 with a 2.92 ERA in 12 appearances.
Reddick was injured Saturday. Melvin said it was necessary to put Reddick on the DL because he is being held out of baseball activities for the duration of Oakland's nine-game road trip.
Brandon Moss returned to the lineup after missing two games with a right calf strain. He was set to be the designated hitter.