Complex sentence: Blackburn Rovers Football Club is a professional association football club in Blackburn, Lancashire, England, which has ompeted in the Championship since being relegated from the Premier League, the top tier of English football, at the end of the 2011--12 season.
Split into simpler sentences: Blackburn Rovers Football Club is a professional association football club based in the town of Blackburn, Lancashire. They were relegated from the Premier League, the top tier of English football, at the end of the 2011--12 season.