According to Nikkan Sports, thirty-eight-year-old Tomoya Satozaki is planning to retire after the season because of left knee problems. The Chiba Lotte Marines have already been notified. A press conference will likely be held on Friday.
Source: Nikkan Sports 9/11/2014
[UPDATE @ 1:14pm]
The Marines posted an announcement on their web site. They also posted the following statement from Satozaki:
I have decided to retire at the end of the season. I won two Nippon Series championships with the Marines and a WBC championship. In looking back at my baseball career, I feel very satisfied. I have no regrets. I was able to have this wonderful career because of the loyal fans, the people involved, and everyone else that gave me support. I am full of gratitude. Thank you for the sixteen years.
Source: official announcement