Prop Paul James says he could miss out on a place in Wales' squad for the tour to South Africa if he does not play in the senior trial match.
Bath's James, 32, has been included in the Possibles squad for the game against the Probables in Swansea.
But England's leading clubs will not allow their Welsh players to take part in the trial match.
"If there's a trial going on and you're not playing in it, of course you're going to be under threat," he said.
The trial match at the Liberty Stadium will help decide who is included in Warren Gatland's final squad for the two-Test tour to South Africa in June.
A total of 52 players have been split between the two squads with six of those players based in England and a further five playing for French clubs.
There has been no definite indication yet whether Welsh-qualified players at French clubs will be available for the trial match, the first to be held by Wales for 14 years.
But a spokesperson for England's Premiership clubs said that because the game is not a Test match they do not have to release non-England players.
The Welsh Rugby Union hopes to reach an agreement with Premiership Rugby, but the trial match takes place the day before the Aviva Premiership final.
James, who has won 53 caps, made five appearances during Wales' 2014 Six Nations matches, coming off the bench in four matches.
The former Ospreys prop, who played in Bath's Amlin Challenge Cup defeat by Northampton in Cardiff, is worried he could miss out on a tour spot by not playing in the trial match.
"I've spoken with Possibles coach Robin McBryde but if boys play in the trial and play well then obviously it's going to jeopardise my position," James added.
"It's out of my hands and I can't do nothing about it. All I can do is sit back, wait and see what happens.
"There's no better place to go than South Africa to test yourself as an international.
"If they're picking a team on form and picking a squad on form hopefully I will be all right."
Probables Squad (coach Rob Howley):
Forwards: Gethin Jenkins (Cardiff Blues), Owen Evans (Dragons), Rhys Gill (Saracens), Ken Owens (Scarlets), Scott Baldwin (Ospreys), Adam Jones (Ospreys), Samson Lee (Scarlets), Alun Wyn Jones (Ospreys) (Captain), Luke Charteris (Perpignan), Jake Ball (Scarlets), Ryan Jones (Bristol), Aaron Shingler (Scarlets), Josh Navidi (Blues), Dan Lydiate (Racing Metro), Taulupe Faletau (Dragons).
Backs: Rhodri Williams (Scarlets), Mike Phillips (Racing Metro), Dan Biggar (Ospreys), Sam Davies (Ospreys), Jon Davies (Scarlets), Jamie Roberts (Racing Metro), Gavin Henson (Bath), Alex Cuthbert (Cardiff Blues), George North (Northampton), Hallam Amos (Dragons), Liam Williams (Scarlets).
Possibles Squad (coach Robin McBryde):
Forwards: Paul James (Bath), Phil Price (Dragons), Rob Evans (Scarlets), Matthew Rees (Blues), Kristian Dacey (Blues), Rhodri Jones (Scarlets), Scott Andrews (Blues), Aaron Jarvis (Ospreys), Bradley Davies (Blues), Andrew Coombs (Dragons), Ian Evans (Ospreys), Macauley Cook (Blues), Josh Turnbull (Scarlets), James Davies (Scarlets), Dan Baker (Ospreys).
Backs: Gareth Davies (Scarlets), Lloyd Williams (Blues), James Hook (Perpignan), Matthew Morgan (Ospreys), Harry Robinson (Blues), Owen Williams (Leicester), Steven Shingler (Scarlets), Cory Allen (Blues), Jonathan Spratt (Ospreys), Tom Prydie (Dragons), Jordan Williams (Scarlets).