After gaining a creditable draw in the hard-fought Champions League semi-final with Barcelona at the Nou Camp on Wednesday, United abandoned their usual strategy of immediately returning to the north-west in favour of staying overnight in Catalonia.
They then flew to London on Thursday night before undergoing a light training session in the capital on Friday morning as final preparation for their title showdown with Chelsea at Stamford Bridge.
"The fixture is not fair in terms of the timing between the two games," said Ferguson.
"Chelsea had a Tuesday fixture followed by a Wednesday one, so they have four days to get themselves ready for both games. There is no question that is a big advantage because, unfortunately, all we have are 60 hours.
"It happened to us last year as well when we came back after the Milan game straight into a lunchtime match with Manchester City.
"It is not fair but once you shake hands with the devil there is nothing you can do about it.
"Really, all we have been able to do is rest the players. Being in the sun and having a day relaxing is probably the best thing we could have done."