Daily Mail · Jan 30, 2019
MARK CLATTENBURG: Referee was right to chalk off Sergio Aguero's second
Manchester City can have no complaints with Paul Tierney for disallowing Sergio Aguero’s goal that would have put them 2-0 up.
At any free-kick, the referee will ask the attacking team if they want to take it quickly.
If that offer is declined, the referee will mark the defensive wall. The attacking team then have to wait for the referee’s whistle before they can take the free-kick.
On Tuesday night, Tierney clearly showed his whistle to De Bruyne — a technique referees use to tell players to wait for the restart. But De Bruyne took it quickly and was booked.