England players are set to miss the British and Irish Lions warm-up match against Japan on 26 June because it is outside World Rugby's Test window.
"At the moment Premiership Rugby have not sanctioned the release of English-based players," Lions managing director Ben Calveley told BBC Sport.
The restriction means Scotland captain Stuart Hogg, who plays for Exeter, would also miss the Murrayfield game.
The Premiership final is on 26 June - the same day as the Lions' warm-up.
However Calveley said he still hoped that an agreement could be reached to allow players from the 10 Premiership clubs not playing in the domestic showpiece to be involved against Japan.
"If there is a way that the players that aren't playing in the final could be made available for the match then clearly we would like that," added Calveley.
"We will continue in dialogue with all of the stakeholders involved.
"Whoever is wearing the Lions jersey will be an incredibly high-quality group of players ready to take on that challenge against Japan."
Hogg's Exeter and Scotland team-mate Jonny Gray and Wales and Bath number eight Taulupe Faletau are also set to be unavailable for the fixture as it stands.
England's players all play their club rugby on home soil with selection of overseas players for the international side only allowed in "exceptional circumstances".
World Rugby stipulates that domestic sides are only obliged to release players to play international fixtures from the first week of July.
The Lions' begin their tour of South Africa against Cape Town-based provincial side the Stormers on 3 July.
The first Test against the world champion Springboks is in Johannesburg on 24 July with the second and third Tests on the following two weekends.
Calveley said he was "absolutely optimistic" that the tour would go ahead despite the difficulties of coronavirus, although admitted that "we are contingency planning in the background in case different scenarios emerge".
The Japan match will be a rare "home" fixture for the Lions.
They drew with Argentina in Cardiff before the 2005 tour of New Zealand, but have attempted to arrange overseas warm-up matches before recent trips.
Japan reached the last eight of the Rugby World Cup on home soil in 2019, advancing from the pools at the expense of Scotland. They also scored a notable victory over South Africa in the 2015 tournament.
"They are a talented side who play high-tempo rugby, so it'll be a good challenge for us," said Lions head coach Warren Gatland.
"It's a chance for the matchday squad to put hands up for Test selection."