Manchester United chief executive David Gill believes the club could have sold more than 100,000 tickets for the Champions League final against Chelsea.
Instead, they will be backed by just over 21,000 supporters in Moscow on May 21 after disposing of Barcelona on Tuesday at Old Trafford.
As Gill prepares to fly to Russia today to meet UEFA officials, he revealed the distribution process was already in place.
'We have actually allocated the tickets broadly in accordance with UEFA instructions prior to knowing whether we would be there,' he told MUTV.
'Our allocation is just over 21,000 tickets and with season ticket holders, box holders and other internal usage, it is a difficult process.
'We could sell well over 100,000 tickets for this final, so there will be a lot of disappointed people.'
The matter of visas will be high on the agenda when Gill meets UEFA officials.
There remain concerns about entry to the country for visiting supporters ahead of an all-English final but he hopes the situation will be clarified in the next few days.
'The visa issue has been there for a while,' said Gill.
'We had discussions with UEFA and the local organising committee along with the other semi-finalists.
'If you are on an organised trip, your ticket will be your visa.
'The actual specifics and fine details will be addressed in the next day or so and then we will communicate with the fans.
'Everyone in UEFA from (president) Michel Platini to the local organising committee recognise in order for it to be a showcase, which it clearly will be, you have to ease entry into the country while not totally doing away with what the Russian authorities require.'
UEFA believe security problems in Moscow will not be a problem for the all-English final - but logistical problems could be faced at the England end in terms of flying all the fans to the Russian capital.
UEFA communications director William Gaillard said: 'The Russians have shown great flexibility and hopefully within the next 48 hours we will be announcing a more simplified procedure for visas to make it easier for fans to get to Moscow.'
Meanwhile, sports minister Gerry Sutcliffe has called on Chelsea and United players and fans to be on their best behaviour and warned any controversies could undermine England's bid for the 2018 World Cup.
Player conduct has been under the spotlight since events following the top-of-the-table clash between the two clubs at Stamford Bridge last Saturday, and Sutcliffe said the eyes of the world would be on the two English clubs on May 21.
Sutcliffe said: 'I was really impressed and pleased that the European champions final will be an all-English final but that brings some responsibilities for the teams involved and their supporters.
'They have to make sure that we have a showcase final, which may help us in terms of our World Cup bid.
'When you think what the global audience will be for the Champions League final, their every move will be watched.
'It should be a great advert for the Premier League and for English football but it will also be the place everyone will be looking at if anything goes wrong.
'If that happened it would not only be damaging for the two teams participating but could also have a big impact on the reputation of our game at a time when we are trying to encourage football nations to support our World Cup bid.'
Sutcliffe has already held talks with Home Office minister Vernon Coaker about ways the police can help the Russian authorities, and will speak to the Foreign Office about facilitating visa arrangements for fans with tickets.