Complex sentence: During the 2013/2014 season he became integral in Manchester United's poor season establishing himself as the worst right-back in the Premier League due to his rash tackling, poor decision making and regular occurrence in the referee's book.
Split into simpler sentences: During the 2013/2014 season he became integral in Manchester United's poor season, establishing himself as the worst right-back in the Premier League. Which was due to his rash tackling, poor decision making and regular occurrence in the referee's book.