Ferguson received a five-match ban for his attack on Martin Atkinson over his handling of the first Premier League game between United and Chelsea in March.

In a game which the United boss felt triggered Chelsea's impressive recent form, Atkinson did not spot a foul by David Luiz that should have brought the Brazilian's dismissal, then awarded the Blues a debatable penalty for Chris Smalling's foul on Yury Zhirkov.

It forms part of what Ferguson feels is a catalogue of key calls that have gone against his team, even though there are a number of examples of United benefiting.

One such occurrence came in January, when Liverpool's Ryan Babel posted a mocked-up picture of Webb on Twitter after an FA Cup third round tie at Old Trafford when the World Cup final referee awarded United a penalty and sent off Steven Gerrard.

"We are getting the best referee, there is no doubt about that," Ferguson said. "But (getting a bad decision) is definitely our big fear.

"We have the players to do it all right. We just hope it's our turn for a little bit of luck."