Peter Abraham writes that, according to Nikkan Sports of Japan, Daisuke Matsuzaka will undergo season-ending surgery on the ulnar collateral ligament of his right elbow (aka Tommy John surgery).
Here is a rough translation of the Nikkon article, with some discussion. Matsuzaka may not have gone to Japan for family reasons, as was reported. He may have received several doses of platelet injection therapy, possibly without the Red Sox's knowledge or approval.
Recovery time from TJ surgery is between 12-18 months. If Matsuzaka has the operation soon (one report says he might have surgery next week), he could conceivably return to the Red Sox at the end of the 2012 season. It seems safer to assume his Boston career is over -- especially if he lied to the front office about the trip to Japan.