Danish side Viborg FF will be without two players for their visit to West Ham in the Europa Conference League play-off first leg because of visa issues.
Ibrahim Said and Alassana Jatta will not travel because of entry rules for non-EU citizens following Brexit.
Viborg said they had "tried everything" and consulted Danish football leaders, Uefa and embassies in both countries.
"We are extremely sorry that we have not been able to get visas for the two players," the club said in a statement.
"Unfortunately this has proved to be impossible, as there is a processing time of several weeks and the match was only finally decided a week ago," they added.
Nigerian winger Said scored in the Danish Superliga side's 2-0 aggregate win over Lithuanian opponents FK Suduva in the second qualifying round - and set up another as they beat Faroese club B36 Torshavn 5-1 over two legs in the third round.
Gambian forward Jatta sealed a 2-1 second-leg win over B36 Torshavn with a goal 13 minutes after being introduced as a second-half substitute.
"It is very unfortunate purely sportingly, as both players would have had a role in the match," said Viborg sporting director Jesper Fredberg.
"But it is even more unfortunate, purely humanly, that the two miss out on the great experience."
West Ham could give defender Thilo Kehrer his debut for the club after the Germany international joined the Hammers from Paris St-Germain on Wednesday.
Morocco international Nayef Aguerd remains sidelined following surgery on an ankle injury he sustained during a pre-season friendly against Rangers, while fellow centre-back Angelo Ogbonna is not yet ready to return from anterior cruciate ligament damage and fellow defender Craig Dawson is a doubt.
Left-back Aaron Cresswell and manager David Moyes are suspended for the first leg and captain Declan Rice is banned from playing in the tie.
The Hammers are one of 44 teams taking part in the play-off round and one of five clubs to have automatically qualified for the stage.
The second leg will take place in Viborg next Thursday, with the winners joining the group stage of the competition when it begins on 8 September.
Viborg must 'keep tie alive' in bid to reach Europa Conference League
A season after being promoted as champions of the Danish second tier, Viborg earned the chance to qualify for the Europa Conference League group stage by securing seventh place in the 2021-22 Superliga.
The club last competed in European competition in 2000, the year they also won their sole domestic trophy, the Danish Cup.
Manager Jacob Friis expects West Ham to have more power than the teams his side are used to competing against, but says Viborg's approach and preparations will not differ markedly from their domestic matches.
"A big and exciting task awaits - not only against a Premier League team, but also a team that played in the Europa League semi-finals and did well in the Premier League last season," Friis said.
"It is indisputably an extremely difficult task ahead of us but we are really looking forward to it. We have to be sharp and are aware that we have a huge task ahead of us."
The former boss of four-time Danish champions AaB Aalborg, who has won 14 of his 25 matches in charge since being appointed in February, acknowledged that his players may have to be at their best and hope their hosts underperform in the first leg.
"A goal must be that the tie is still alive after the first match," he said.
"We need luck to be on our side. If all that happens, it can start to look like something for us."
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