Marmix, you are aware that wagering on sporting events (such as MLB) is illeagal except in the state of Nevada (in the US) so declare your "winnings" could be construed as conducting illeagal activities and open you up to jail time.
Why would you ever declare anything at all ever, unless you live and Nevada and can gamble legally?
You simply withdraw money via western Union and MoneyGram in moderate amounts spread out over weeks and months and don't worry about it