Most Single Season Losses

1. Detroit Tigers 43 (2003)
2. Arizona Diamondbacks 51 (2004)
3. Detroit Tigers 55 (2002)
-- Tampa Bay Rays 55 (2002)
5. Kansas City Royals 56 (2005)
-- Milwaukee Brewers 56 (2002)
7. Kansas City Royals 58 (2004)
8. Washington Nationals 59 (2008)
-- Washington National 59 (2009)
10. Seattle Mariners 61 (2008)
--- Tampa Bay Rays 61 (2006)