Former Premier League referee Keith Hackett is 'concerned' Michael Oliver could leave English football after he was spotted refereeing in Saudi Arabia during the week.
Oliver took charge of the game between Cristiano Ronaldo's Al-Hilal and Al-Nassr in Riyadh on Tuesday - four days before taking charge of Liverpool's Premier League clash with Nottingham Forest at Anfield.
The 38-year-old is consider the Premier League's best official and was one of just two referees from England to be selected for the World Cup in Qatar.