Complex sentence: As of 2011, the Buffalo Bills are the only team in the National Football League to have not yet made the playoffs in the 21st century, a distinction shared with the Houston Texans and Detroit Lions until both of those teams made the playoffs in 2011.
Split into simpler sentences: As of 2011, the Buffalo Bills are the only team in the National Football League to have not yet made the playoffs in the 21st century. The other two teams who hadn't made the playoffs in the 2000s--the Houston Texans and Detroit Lions--both made the playoffs in 2011.