Riley booked seven United players during the 1-1 draw with Chelsea.

The visitors were lucky the damage was not even worse given Cristiano Ronaldo got away with a blatant dive just after his introduction as a second-half substitute and Rio Ferdinand appeared to charge right into Didier Drogba as Riley blew for full-time.

As both Ronaldo and Ferdinand were among the seven offenders, United could easily have been cursing a red card as well as the glut of yellows which leaves them facing an automatic FA fine.

Yet Ferguson did not believe there had been a bad tackle in the game.

"The game is being screened worldwide," he reflected.

"Everyone is watching it and something like that goes on.

"It was a competitive game but I did not think there was one bad tackle in it."

Apart from Ferdinand and Ronaldo, Paul Scholes, Dimitar Berbatov, Gary Neville, Wayne Rooney and Patrice Evra were cautioned.

"People are saying, 'What is going on here?' but it is difficult to say anything about the referee," added Ferguson.

"I do not want to get involved."

United's players clearly felt the same way as their manager as they left Stamford Bridge, although Riley's performance is sure to get dissected by the FA before they take action.

The number of bookings - Chelsea had one as well - certainly went against the principles of the FA's much-trumpeted 'Respect' campaign.

"I am not surprised," said Luiz Felipe Scolari.

"That is what the referee is there for.

"If players do not respect him, it should be yellow and red cards. It doesn't matter who you are - Liverpool or Manchester United, whoever."

However, the Chelsea coach said he was puzzled at the bizarre ending, with Riley blowing for time as Drogba was about to receive treatment.

"It was strange that he finished the game at that time but we need to accept his decision."