Complex sentence: Since 2005, no incumbent holder has managed to successfully defend their title, in fact between 2006 and 2013 every defending Super Bowl champion would conclude the following season either losing their opening playoff game or failed to qualify for the playoffs.
Split into simpler sentences: Since 2005, no incumbent holder has managed to successfully defend their title. In fact between 2006 and 2013 every defending Super Bowl champion would conclude the following season either losing their opening playoff game or failed to qualify for the playoffs.