Former Wales captain Ryan Jones' World Cup participation is in doubt because of his calf injury.
Coach Warren Gatland is pondering calling in a replacement for the back-five forward.
Like Stephen Jones and Gethin Jenkins, Ryan Jones has a calf problem that may not clear up for two more weeks.
That means the Ospreys' back-five forward might only be fit for Wales' final Pool D game against Fiji on Sunday, 2 October in Hamilton.
Gatland will wait until the aftermath of Wales' tournament opener against South Africa on Sunday to consider what course of action to take over the Ospreys forward.
The 30-year-old has yet to feature in a World Cup, having missed the 2007 tournament with a shoulder injury.
Following his announcement of the team to face the Springboks this weekend, Gatland said: "We just want to see how Sunday goes.
"Hopefully we don't pick up any injuries and we've just got to give that injury [to Ryan Jones] a little bit more time to settle.
"The thing is if we do replace a player then if he does recover in two weeks and you pick up another injury, you can't recall that [original] player.
"So it's a long tournament and we've got to make sure that we make the right decision there.
"And can we give him enough time? Obviously if we pick up injuries on Sunday… it may change our thinking so we'll wait to see what happens."
Danny Lydiate, who will fill the blindside flank role that Ryan Jones has sometimes occupied is sympathetic to his squad-mate's plight.
Lydiate said: "I'm just gutted for him really. He's trained this week and the enthusiasm he has when he's out here especially with us younger boys is great.
"He takes you under his wing and he's brilliant and he has his little words of wisdom that you really listen to.
"So just gutted for him and hopefully he can recover and it's not as bad as it seems."
Wales team manager Alan Phillips had earlier declared that of Stephen and Ryan Jones the latter was more likely to be fit to face the Springboks.
Fly-half Stephen Jones and prop Jenkins could, however, come into contention to face Samoa in Wales' second game on Sunday, 18 September in Hamilton.
Gatland named Jenkins in his 30-man squad, even though the 30-year-old loose-head has had injury problems since January.
Ryan Jones rested his calf when Wales beat Argentina 28-13 at the Millennium Stadium last month.
Wales also suffered injuries to key players in the build-up to the World Cup, which kicks off on 9 September when hosts New Zealand take on Tonga in Auckland.
Versatile Morgan Stoddart was ruled out with a broken leg, centre Gavin Henson suffered a wrist injury in a warm-up game against England in Cardiff and front row Matthew Rees followed medical advice to have surgery on his neck.
