Wales fear that Ospreys wing Eli Walker could miss the whole of their autumn campaign after injury cruelly denied him a Test match debut against South Africa.
Walker will be replaced by Scarlets back Liam Williams at the Millennium Stadium on Saturday, with Ospreys centre Ashley Beck taking Williams' bench spot.
It is terrible luck for the 21-year-old, who had been set to fill the void created by injured British and Irish Lions wing Alex Cuthbert.
"We are fearing the worst, but I am sure the scan results will point us in the right direction," Wales assistant coach Rob Howley said.
"Eli pulled up this morning with a hamstring strain. We are not too sure whether it is a grade one or grade two. We will await the results of the scans and the likelihood that he might not be available for the whole of the autumn series, which is a blow to us.
"He has come in with good form. I just feel so desperate and gutted for the player himself," Howley said.
"Eli is pretty disappointed. This happened last season and the problems he had throughout the summer with his back and hamstrings. You feel for him.
"He is a fantastic kid and he has added so much to our environment. He tried to beat someone in training, he came off his right foot and accelerated out of the contact and just felt that bit of a twinge."
Howley fronted Thursday's Wales press conference, replacing head coach Warren Gatland, who had been scheduled to make his first media appearance of the week.
Asked about the New Zealander's absence, Howley said: "At this moment in time he (Gatland) is meeting some of our players. He is unavailable and that's all."
Quizzed further on whether or not Gatland's no-show could have been in relation to some off-the-record comments he made during a dinner earlier this week subsequently being reported, Howley said: "I am unaware of that."
On the field, Wales know they must address a dreadful record against South Africa that epitomises their long struggle to claim major southern hemisphere scalps.
They have only beaten the Springboks once from 26 attempts, while Wales last beat New Zealand 60 years ago and have not toppled Australia since 2008.
That record has proved in stark contrast to their considerable achievements under Gatland of reaching a World Cup semi-final, winning three Six Nations titles and two Grand Slams.
"Playing under pressure is going to be key on Saturday," Howley said.
"We feel that in our Lions players selected we've got experience, and it is going to be a great game to watch. It won't be for the faint-hearted.
"The roof is going to be closed, so hopefully it is going to be a nice dry park and we can play some rugby.
"South Africa have got experience throughout their side. I thought they would bring back Jaque Fourie, he is a talisman for them. His (midfield) partnership with Jean de Villiers is obviously going to be critical to how they play, both in attack and defence.
"It is important to earn the right to play in the wide channels that we want to do.
"It is going to be an arm wrestle, however long that arm wrestle goes on for. I think that is the nature of international rugby when two world-class outfits come together."
While Wales play their first Millennium Stadium Test since destroying Grand Slam-chasing England by a record 30-3 scoreline almost eight months ago, South Africa arrive as Rugby Championship runners-up.
The Springboks won four of their six games in that competition, averaging almost four tries a match, and Meyer fields 10 of the team that started a stunning Championship decider against New Zealand in Johannesburg five weeks ago.