Taulupe Faletau is "under pressure" not to move to Bath from Newport Gwent Dragons, says former Wales and Dragons fly-half Ceri Sweeney.
Wales boss Warren Gatland has suggested he would not sanction such a deal.
That would put the Test future of the British and Irish Lions number eight, 24, in doubt if he did move to England.
"He's one of the first names on the team sheet and I wouldn't be surprised if Wales are putting him under a bit of pressure to stay," Sweeney said.
"He's thinking ahead for his future... whether he feels that he'll go to this  World Cup and that will be his lot, only he can answer that.
"But that could be one of the factors in him going over there [to Bath].
"There's a lot of different factors... it isn't taken lightly on the player's behalf, I know that... it's a big decision that he has to make while he's thinking about his future."
If Faletau were to join Bath after this year's World Cup, his chances of playing for Wales in future could be restricted.
Under the Rugby Services Agreement Gatland can only select two players who are based outside of Wales, although this does not include those who were already abroad before the new deal between the WRU and the four Welsh regions was signed in August 2014.
But Sweeney, who rejoined Welsh Premiership side Pontypridd after leaving Exeter Chiefs in May, thinks that Gatland was left little choice but to refuse to sanction Faletau's proposed move to the Rec.
"Coming from Warren Gatland's side of it, he cannot be seen to sanction another player leaving and going over the [Severn] Bridge to play his rugby in England," Sweeney, 35, told BBC Radio Wales Sport.
"The big thing with the Welsh regions and the players at the moment is they have got a lot of control over them.
"They get them when they want them for training camps and they get that little bit of extra time with them that seems to work.
"So to lose another one of their star players... is not good for Welsh rugby really.
"It does put that onus back on the player then, that if he does leave Wales his international future could be in jeopardy.
"It's a big decision now. The Welsh Rugby Union has got to take a stance on it because... people want to watch the best players on the field playing in Wales."