Complex sentence: Blackburn Rovers Football Club is a professional football club in Blackburn, Lancashire, England, whcih competes in League One, the third tier of the English football league system, following relegation from the Championship at the end of the 2016--17 season.
Split into simpler sentences: Blackburn Rovers Football Club is a professional association football club based in Blackburn, Lancashire, England. The club competes in League One, the third tier of the English football league system, following relegation from the Championship at the conclusion of the 2016--17 season.