Coach Warren Gatland has warned players based outside Wales they may be left out of his Six Nations plans.
Gatland "ideally" wants his players 13 days before their 2012 opener against Ireland on Sunday, 5 February.
Mike Phillips, James Hook, Lee Byrne, Craig Mitchell and Andy Powell play in France or England and their clubs play the weekend before the Dublin clash.
"If those [exiled] players can't get full release for the Six Nations then they won't be selected," said Gatland.
The quintet are absent from the Wales squad to face Australia in Cardiff on 3 December. That game is not being played in an International Rugby Board window.
Wales' regions have an agreement with the Welsh Rugby Union that their players are available for all the national team's commitments, including almost two weeks of preparation ahead of tournaments, tours and autumn Tests.
Unlike Welsh teams, clubs outside Wales do not have to release players almost two weeks ahead of internationals.
On the weekend before Wales take on Ireland, Phillips' Bayonne are at Toulon in the French Top 14, Hook could be on Perpignan duty at Brive and Clermont Auvergne, where Byrne is employed, are at Bordeaux-Begles.
Prop Mitchell could be in action for Exeter at Wasps in the LV= Anglo-Welsh Cup, with Andy Powell likely to line up for Sale Sharks at Newcastle in the same tournament that weekend.
Gatland admits there are "one or two players" who were not wanted by other Welsh regions when they left their former employers in Wales.
He will be mindful of that situation when selecting for Europe's international showpiece in February.
"There've been one or two that have left Wales because they haven't been wanted by the other regions and we've got to be mindful of that as well," said Gatland.
"I think we need to be a bit careful with one or two that it would depend on, we're not going to put ourselves in a corner if we've got injuries in certain positions."
However, Gatland is unimpressed that some players who have taken up contracts outside Wales did not ensure they would be available for international duty.
Gatland added: "So [I'm] disappointed to hear that a couple of them had verbal agreements, but not written in their contracts which I'd sat down with them to do.
"So we're just being consistent on that, but that gives a great opportunity for some of these youngsters coming through that have been really impressive.
"But there is a warning out there if you're going to leave Wales, make sure that you've got it in your contract that you've got full release for all Welsh games and squad sessions.
"Because if you don't you aren't going to get selected, so it is a bit of a concern for us going forward."
Cardiff Blues' Lloyd Williams, team-mate prop Scott Andrews, Ospreys' fly-half Dan Biggar and Scarlets' back-three player Liam Williams could benefit respectively from the absences of Phillips, Mitchell, Hook and Byrne from the squad to face Australia.
Mitchell's absence at tight-head is compounded by Adam Jones' calf problem that has left Andrews with the chance to prove his potential in a squad littered with injury doubts.
Gatland admitted Jones' injury is an issue "with Craig Mitchell not available to us".