Sam Costelow is facing an injury lay-off after damaging both his shoulder and hamstring.

The double injury is thought to be significant, leaving both club and country looking at alternatives for the number ten jersey.

Wales head coach Warren Gatland said he has already considered converting scrum-half Tomos Williams to the role.

Costelow had appeared to be the immediate choice to step into the fly-half berth vacated by the retirement of Dan Biggar and departure of Gareth Anscombe to Japan.

The 22-year-old made his first Test start in the summer friendlies against England and again against South Africa and appeared in four of Wales' five games at the World Cup.

He played a key early role against Barbarians but was clearly grimacing when he scored Wales' third try just before half-time and did not emerge for the second half.

Scarlets head coach Dwayne Peel said: "I am concerned about Sam because he's one of our key players. He's been excellent and grown into a leader for us.

"I had a text off him to say he was pretty sore. He has both shoulder and hamstring [injuries] so it never rains but it pours on the injury front for us. We have to wait for the scan results."

Tomos Williams option

Gatland is scratching around for options having lost six contenders for the Wales number ten jersey in a matter of months.

As well as World Cup pair Biggar and Anscombe, Rhys Patchell, Joe Hawkins and Jarrod Evans have made themselves ineligible for selection after moving to clubs outside of Wales.

Rhys Priestland left Cardiff at the end of last season and indicated he is unlikely to play again.

Cardiff's Williams was pressed into action as a makeshift fly-half for the last ten minutes against Barbarians but Gatland revealed they had already considered that move before the World Cup.

"We trained against Scarlets and Tomos played at 10 and he really impressed us," said Gatland.

"It was out of necessity because we had injuries but he looked really comfortable there and we talked about his potentially being an option as a replacement.

"We saw [against Barbarians] how comfortable he is on the ball and his decision-making, passing and spatial awareness are all excellent. Apart from a brain freeze in terms of a lineout dropout, I thought he was good.

"It's a potential opportunity for us to have a bit more depth and cover in certain positions. I'm not saying we're definitely going to do that, but it'll be part of our discussions."

Gatland's search

Gatland said he will hit the road in search of "more options" for the position, including watching Bristol's 16-cap Callum Sheedy as well as Dragons youngster Will Reed and will push for Cardiff to hand centre Ben Thomas a chance in the position.

Meanwhile Peel talked up the promise of Ioan Lloyd after kicking 11 points in a commanding performance in Scarlets' 31-25 win over Cardiff.

"He is growing every week in that number 10 shirt but he controlled this for us," said Peel.

"There is going to be a lot of work for him to do after being moved around for Bristol but that was his best game for us."