The Red Sox expect Daisuke Matsuzaka to be out for a minimum of a month after he was diagnosed with a sprained ulnar collateral ligament and strained flexor, an injury that when severe enough often results in Tommy John tendon transfer surgery. The team is hoping that Matsuzaka will be able to avoid the surgery, which would sideline him for the rest of the season, and that he will respond to rehabilitation, according to a club source.