United's overall income for the first three months of the financial year was £88.7m, down £9.8m, but the club did record a profit of £8.9m.
Failure to qualify for this season's Champions League meant big reductions in both broadcasting and match day revenue, down 13% and 21.8% respectively, while money from commercial activity was down 5.2%.
But the lack of European football did not prevent United securing a record kit deal during the quarter, and chief executive Ed Woodward predicted further "growth opportunities" as the financial year progresses.
He said: "While we recognize that the 2014/15 fiscal year financial results will reflect our absence from the Champions League, we signed the largest kit sponsorship deal in the history of sport in the first quarter.
"With that concluded we are excited to focus our efforts on the meaningful growth opportunities in sponsorship, digital media and retail and merchandising."
Sports business consultant David Bick told Sky Sports News HQ the results should be of concern to the club's shareholders and warned a prolonged spell out of the Champions League would have a knock-on effect on the £750m Adidas kit deal that kicks in next summer.
He said: "Certainly it's a record deal, worth an average of £75m a year, but there will be a rub and that is there will almost certainly be a penalty clause in that contract in the event that they don't qualify for the Champions League.
"Last season they earned 47-8m euros just from the additional media rights, then you have to add on matchday revenue and commercial revenue.
"If they don't qualify I think that Adidas deal will come down quite considerably, and it won't compensate for the loss of the other side of the revenue. It comes back to the fundamental - if you're normally a regular Champions League participant then being out of it carries severe financial penalties."
Manager Louis van Gaal has suggested it might take three years to revive United. Bick said: "My anaylsis suggests if you're out (of the Champions league) for more than two years it starts to have a very serious impact. In purely financial terms they can't afford to wait three years."
