Complex sentence: After sacking Sam Allardyce as the club's manager, Venky's oversaw an unsuccessful period with Steve Kean in charge, resulting in relegation to the Championship at the end of the 2011--12 Premier League season ending 11 years of being in the English Premier League.
Split into simpler sentences: After sacking Sam Allardyce as the club's manager, Venky's oversaw an unsuccessful period with Steve Kean in charge, resulting in relegation at the end of the 2011--12 Premier League season. The club was relegated to the Championship at the end of 2011-12 season, ending 11 years of being in the English Premier League.