Gavin Henson's hopes of going on trial with Wales before a two-Test South Africa tour next month look likely to be dashed.
Bath centre Henson, 32, has not played for Wales since he was injured during a Millennium Stadium warm-up game against England just weeks before the 2011 World Cup in New Zealand.
Henson and four other players with Aviva Premiership clubs have been named among 52 selections across 26-man Probables and Possibles squads for an official Wales trial match in Swansea on May 30.
Wales head coach Warren Gatland will then announce a 31-strong tour squad during his post-match press conference at the Liberty Stadium.
The Welsh Rugby Union are in contact with English and French leagues - Jamie Roberts, Mike Phillips, Dan Lydiate, James Hook and Luke Charteris all play in the Top 14 - about potential availability for the trial.
Racing Metro trio Roberts, Phillips and Lydiate, though, plus Northampton wing George North, Leicester fly-half Owen Williams and Saracens prop Rhys Gill could be involved in May 31 domestic finals and would therefore be off-limits anyway.
And new Bristol recruit Ryan Jones has potential Rugby Union Championship play-off final commitments across two legs on May 29 and June 4.
English and French clubs are not obliged to release non-English or non-French players as the trial fixture is not a Test match, as stipulated by the International Rugby Board.
North, though, does have release in his Saints contract for all Wales duties.
"Premiership Rugby has a policy to only release non-England players under the conditions of IRB Regulation 9," a Premiership Rugby spokesman told Press Association Sport.
"This regulation covers international release for every Test country across the world.
"This trial match does not fall under IRB Regulation 9."
Gatland, meanwhile, is resigned to be being without several injured players for Tests against South Africa in Durban and Nelspruit, while Wales will also face the Eastern Province Kings in Port Elizabeth on June 10.
The list of absentees includes Sam Warburton, Leigh Halfpenny, Justin Tipuric, Scott Williams and latest addition Rhys Priestland, who suffered a knee injury in RaboDirect PRO12 action for the Scarlets three days ago.
Gatland said: "We have been in contact with Premier (Premiership) Rugby to say we are going to name the players in the squad, and we are just hoping that common-sense prevails and those players that are finished for the season are released.
"We understand they've got a board meeting next week, so we are hopeful that those players are going to be released.
"I can understand Premier Rugby at certain points protecting their competition and that, but to me, I don't understand when players are finished for the season why they wouldn't be released and be available to us and for them to have an opportunity to be selected and play international rugby
"I think it's good for the game, I think it's good for the English clubs and the English Premiership to release those players and increase their profile. Hopefully, there is some goodwill in the game and then these players will be released.
"We want to make sure this trial has real teeth.
"It's important that players will be selected on their performance. But we will also consider what we know about them and how they've performed in the past."
Gatland's assistant and Probables head coach Rob Howley has named two uncapped players in his squad - Ospreys back Sam Davies and Newport Gwent Dragons prop Owen Evans - which will be skippered by tour captaincy favourite Alun-Wyn Jones. Henson is also among that group.
And there are 10 uncapped players in a Possibles squad led by hooker Matthew Rees, including Tigers prospect Williams, plus promising Cardiff Blues forwards Kristian Dacey and Macauley Cook.
"The trial is a great platform for us to see all of these players up close and allow them to pit themselves against each other," Howley said.
"It takes us back to the traditional Wales trials of old, and gives players an opportunity to put their hand up for the Wales jersey. Both sides will be going hard against each other with players having a point to prove.
"It's also a vital game in our preparation ahead of the tour to South Africa. The vast majority of the squad wouldn't have had any game time after last weekend, and this allows us to have a meaningful match."