Wales fly-half Sam Costelow is expected to be sidelined until January after suffering shoulder and hamstring injuries.

Scarlets playmaker Costelow was hurt during Wales’ 49-26 victory over the Barbarians on Saturday and went off at half-time.

He is a clear favourite to succeed Dan Biggar, who retired from Test rugby after the World Cup, in Wales’ number 10 shirt.

Wales kick off their Six Nations campaign against Scotland in Cardiff on February 3.

“We are not expecting him in the short term,” Scarlets head coach Dwayne Peel told reporters ahead of Saturday’s United Rugby Championship clash against South African side the Lions.

“It will be beyond Christmas, beyond the new year before we see him. I haven’t an exact date. We are still waiting on the final prognosis and some specialist opinion, really, on that.

“It is a disappointing one for us because he is going to be out for the large part of the first half of the season.

“There is loads more to come from him, and this is obviously a setback in his career at the minute to have this injury.”

Costelow impressed for Wales at the World Cup in France, starting the pool game against Georgia when Gareth Anscombe was a late withdrawal.

And he is the latest member of that squad to be sidelined, with Exeter forward Christ Tshiunza suffering a broken foot on his return to domestic action and number eight Taulupe Faletau continuing his recovery from a broken arm sustained in the Georgia match.

Wales, meanwhile, are without the Six Nations services of Anscombe and full-back Liam Williams, who will play domestic rugby in Japan next year.

Wales say that fly-half talisman Dan Biggar is fit for the Rugby World Cup quarter-final clash against Argentina on Saturday.

Biggar went off after just 12 minutes of Wales’ record 40-6 win against Australia during an unbeaten march through Pool C.

He suffered a pectoral muscle strain and was an unused replacement for the Georgia game last weekend, having been rushed on to the bench when Sam Costelow was summoned to start instead of an injured Gareth Anscombe.

When asked if Biggar was fit to face the Pumas in Marseille, Wales assistant coach Jonathan Thomas said: “Yes.”

There is also encouraging news about Anscombe and full-back Liam Williams.

Anscombe withdrew 45 minutes before kick-off against Georgia due to a groin problem, while Williams was on crutches after taking a blow to his knee.

Those issues came on top of number eight Taulupe Faletau breaking his arm and being ruled out of the tournament remainder.

“At this stage, it is looking positive,” Thomas said, of Anscombe and Williams. “Every day it will evolve. It is probably not as bad as first feared.

“The crutches thing was to try and offload any pressure. It doesn’t mean he (Williams) has done anything severe. He was jogging about today with the medics.

“I saw him (Anscombe) jogging around on the pitch, along with Liam today.

“The first 48 hours after you have a knock is very important in terms of assessing it. With both Liam and Gareth, it is pretty positive.

“That is not me committing to saying they are definitely going to be available. It is an ongoing thing. They were both running around today with the medics, and they will try to progress that each day.”

Wales head coach Warren Gatland is due to name his starting line-up on Thursday, with Aaron Wainwright expected to move from blindside flanker as Faletau’s replacement.

That could then mean captain Jac Morgan wearing the number six shirt and Tommy Reffell starting at openside, although Dan Lydiate and Christ Tshiunza could also be back-row options.

Thomas added: “There was definitely a little bit of a cloud over the victory (against Georgia) because of what happened to Taulupe.

“We have been together for a long time as a whole group, and you build relationships and you become a little bit like a family. When one of your brothers has to leave, it is tough.

“It is what it is. You have got to deal with it and you have got to move on. That is sport and the harsh reality of it.”

Wales face Argentina for the first time in a World Cup game since 1999, and they will start as favourites after collecting 19 points from a possible 20 in their group.

Argentina, in contrast, lost to 14-man England and were unconvincing against Samoa, before clinching qualification by beating Japan.

“For us as a collective, our goal from day one has been to get to knockout rugby,” Thomas said.

“We have achieved that, but we are not satisfied with just getting to the quarter-finals.

“When you get to this stage, any team on their day can beat anyone. There are quality teams and quality players in the last eight.

“I thought they (Argentina) looked more cohesive in their last game against Japan in terms of their attack.

“If you win your first game in the Six Nations, momentum is huge, and it is the same with the World Cup. Every team at this stage will feel confident and feel they have momentum on their side.”

Wales were left to count the cost of their Rugby World Cup victory over Georgia after number eight Taulupe Faletau suffered a broken arm and two other players were also injured.

Faletau, who has won more than 100 caps, will take no further part in the tournament as Wales build towards a quarter-final against probably Argentina or Japan in Marseille next weekend.

Wales head coach Warren Gatland said no decision had yet been made on a replacement for Faletau, although flanker Aaron Wainwright is an option to move across the back-row.

Fly-half Gareth Anscombe, meanwhile, withdrew 45 minutes before kick-off in Nantes following a groin problem suffered during the warm-up.

And full-back Liam Williams was on crutches after Gatland said he took a blow to his knee, but Wales are hopeful he will be fit for the quarter-final, with Wales ending their Pool C campaign as group winners with four successive victories following a 43-19 triumph.

“Toby (Faletau) has broken his arm so he will be out,” Gatland said.

“We are just going to assess Gareth over the next 72 hours. He has pulled his groin very high up.

“Talking to the medics, he has got a bit of power still in his leg which is a positive. It means he has not pulled it off the bone.

“We will probably know in the next 48-72 hours what we need to do with him. Whether we’ve got (time) for him to recover or replace him directly.

“We have got to look at a replacement for Faletau, whether that is directly as a loose-forward replacement or whether we look at another position.

“We’ve got a few sore players, particularly in the backs, after today’s game.

“If you do see Liam Williams on crutches, it is not that he has done anything significantly bad.

“He got a whack on the knee, and the medics, from a comfort perspective, have put him on crutches to save him walking around a bit.

“He has got a knock and probably won’t take a huge part in training in the early part of next week, but hopefully he will be fit for the quarter-final.”

Jonathan Humphreys says that Wales “cannot afford to go off-script” when they tackle Rugby World Cup opponents Georgia in Nantes on Saturday.

Wales need a point from their Pool C finale to win the group, having already secured a quarter-final place through beating Australia by a record 40-6 scoreline nine days ago.

They lost 13-12 at home to Georgia when the countries last met almost a year ago, and Wales assistant coach Humphreys has emphasised a fierce sense of determination in the camp.

“There has been a bit of an edge about training, which is what we want,” forwards specialist Humphreys said.

“We are just keen to continue the progress that we’ve shown. That is a big driving force for us, and we have talked constantly about that.

“I expect them (Georgia) to play a bit, and they are strong up-front – we are under no illusion about that.

“They are a dangerous outfit, and we cannot afford to go off-script.”

Few could have imagined Wales reaching the last eight just 11 months after Georgia triumphed 13-12 in Cardiff, and Humphreys added: “We’ve had five months together. We are more like a club team than an international team.

“We came in earlier than most teams, we know what we wanted to improve and we haven’t deviated from that.

“Probably the messages that went out in May, they haven’t changed at all.

“Every day, it has been working on those fundamentals that we felt were important and would make a difference.”

Wales head coach Warren Gatland has made six changes for the Georgia clash, with Dewi Lake captaining a side that also sees starts for wing Rio Dyer, fly-half Gareth Anscombe, scrum-half Tomos Williams, lock Dafydd Jenkins and flanker Tommy Reffell.

Centre Nick Tompkins will continue his midfield partnership with George North, meanwhile, and look to maintain the form that has made him among Wales’ most impressive performers at the tournament.

“We want no dip in our performance,” Tompkins said.

“We want to get better, we don’t want to take our foot off the pedal – that’s the last thing we want. We want confidence and momentum and to keep on going.

“I want to just keep getting better and keep pushing myself. There are a lot of things I need to improve on.

“I am happy with some areas, but there are some things I really need to push myself on.

“You look at some of the other centres out there and how well they are doing, and you want to emulate that.

“Being together as a squad for five months means you can have those little conversations and make little tweaks.

“You are all looking for little things to tweak and improve. It has been really healthy, and it has been all of us pushing each other.”

Tompkins has also voiced his support for the World Cup bunker system, whereby incidents of foul play can be referred and a yellow card retained or upgraded to red.

“I like it,” Tompkins added.

“Decisions are tough at the moment anyway, referees are under a lot of a pressure to keep the game moving quickly and get the right decision.

“I think it is brilliant, I like that model. To cut down the pressure we put on referees, especially, is good.”

Gareth Anscombe has revealed how he feared his Rugby World Cup hopes might have been destroyed by injury for a second successive tournament.

The Wales fly-half missed Japan 2019 after suffering an horrific knee injury during a World Cup warm-up game against England that sidelined him for two years.

Anscombe fought back to put himself on the international stage once more – then injury struck again during Wales’ World Cup training camp in Turkey earlier this summer.

An attempted tackle on George North left Anscombe with a thumb problem that resulted in scans and him having to wear a plaster cast for a month, ruling him out of Wales’ three pre-World Cup Tests.

“I suppose I had a night there in Turkey where I thought I was done again, and that was devastating,” said Anscombe, who starts Saturday’s Pool C clash against Portugal at Stade de Nice.

“You have some dark thoughts then, but thankfully I had some luck on my side for once.

“It didn’t look great at the start, and the initial prognosis was it was probably going to need surgery, but thankfully the scans came back better than first thought.

“I had to be in a cast for a month, which was difficult, but at least I could still run.

“I missed the warm-up games, but to have the backing of the coaching staff was great. They spoke to me and said I was still in their plans, which was nice to hear.

“It has been about getting myself right and ready for when an opportunity presented itself, and here we are this weekend.”

Anscombe is one of eight survivors from Wales’ 2015 World Cup squad to be involved eight years later, and he offers considerable experience through 35 caps.

And the New Zealand-born number 10 is relishing a chance to play his part as Wales aim to reach the World Cup knockout phase for a fourth successive tournament.

He features in a team showing 13 changes from the side that toppled Fiji, and it is Anscombe’s first World Cup appearance since he started at full-back against quarter-final conquerors South Africa eight years ago.

“We know there are parts of our performance that we need to improve if we want to progress deep into this tournament,” he added. “But it was a great start (against Fiji).

“There has been an element of confidence brewing. The more time we spend together, we always improve.

“You look back to the Six Nations, a new coaching group and a fairly volatile situation in Welsh rugby.

“We’ve just been able to get away from a bit of the noise, which I think has been important for us as a group. Getting away in Switzerland and Turkey, focusing on ourselves.

“You always need an element of luck in World Cups, with injuries and decisions. We just hope to slowly go about our work and ride the wave.

“We had fantastic support on the weekend. I think more people will jump on the plane over and get behind us. I think you see when Welsh fans get behind us, who knows what can happen.”