Former Wales captains Phil Bennett and Kingsley Jones believe Lee Byrne could miss out on World Cup selection.
Byrne, the only specialist full-back in Wales' preliminary Cup squad, made his solitary warm-up appearance in Wales' 28-13 win over Argentina on Saturday.
"[Byrne is] possibly a player that's played himself out of the trip," said former flanker Jones.
"We have to be brutal with him, we're in a professional world," said 1970s fly-half legend Bennett.
"I thought [wing] Leigh Halfpenny, he didn't have a lot of ball, but what he did show was a work-rate.
"He chased everything and he worked his socks off.
"Lee Byrne... was a man who badly needed a big game and he didn't produce that game."
However, if Gatland leaves Clermont Auvergne-bound Byrne out of the 30-man party he announces on Monday, he will be left with some relatively untried options at the back.
Halfpenny has also played at full-back, but is primarily a wing and James Hook has been Wales' most recent regular stand-in full-back.
Bennett and Jones were part of the BBC Radio Wales commentary team at the Millennium Stadium.
Bennett added: "It's going to be very interesting - will Gatland go on his [Byrne's] past reputation... or does he look for guys like Rhys Priestland to fill in there, Leigh Halfpenny to fill in the position?"
Former Llanelli, Wales and British and Irish Lions star Bennett also believes Hook may be needed at inside centre.
He fears Jamie Roberts and Jonathan Davies are too similar in attack and would not trouble the major powers at the tournament.
"I feel sometimes they're [Roberts and Davies] too similar, too alike - two big men, two powerful men, great in defence.
"Sometimes you're looking for somebody to open that up and whether it's James Hook at inside centre or somebody with a little bit of skill and vision I do not know.
"But I would look at the top teams in the world and I don't think they would be frightened by that kind of attack."
Wales' preliminary World Cup squad
Forwards: Scott Andrews, Gethin Jenkins (Blues), Lloyd Burns (Dragons), Huw Bennett, Ryan Bevington, Richard Hibbard, Adam Jones, Paul James (Ospreys), Ken Owens, Craig Mitchell (Exeter), Bradley Davies, Sam Warburton, Martyn Williams (Blues), Luke Charteris, Danny Lydiate, Toby Faletau (Dragons), Ryan Jones, Alun Wyn Jones, Jonathan Thomas, Justin Tipuric (Ospreys), Josh Turnbull, (Scarlets), Gareth Delve (Melbourne Rebels), Andy Powell (Sale Sharks).
Backs: Michael Phillips (Bayonne), Lloyd Williams (Blues), Tavis Knoyle (Scarlets), Jamie Roberts (Blues), James Hook (Perpignan), Jonathan Davies, Stephen Jones, Rhys Priestland, Scott Williams (Scarlets), Leigh Halfpenny (Blues), Lee Byrne (Clermont Auvergne), Aled Brew (Dragons), Shane Williams (Ospreys), George North (Scarlets).