Wales scrum-half Rhys Webb out of Six Nations

Rhys Webb toured New Zealand with the 2017 British and Irish Lions, playing in two Tests

Wales scrum-half Rhys Webb has been ruled out of the Six Nations with a knee injury.

The omission of the 31-times capped Webb adds to Wales' already lengthy injury list.

Head coach Warren Gatland has eight front-line players missing for the opening match against Scotland on 3 February and major doubts over at least three others.

Cardiff Blues' uncapped Tomos Williams has been added to the squad.

Webb, who leaves Ospreys to join Toulon at the end of the season, will be assessed to establish what treatment he requires.

Williams joins Scarlets' duo Gareth Davies and Aled Davies as Warren Gatland's Six Nations scrum-half options.

Webb devastated

Webb said he was "devastated" to leave the squad with what he described as a "slight knee issue".

"I could have stayed and managed my knee in camp but I [know] for me personally and for the team to win the Championship I couldn't do that," he said on his Twitter account.

Webb's move to Toulon means he will not be eligible for Wales next season under new selection criteria and so may not add to his 31 caps.

The new rules mean only players with more than 60 caps can be selected if they play their domestic rugby outside Wales.

Gatland's team tour Argentina in the summer when Webb will still be eligible, but he will still be a long way short of the selection threshold.

He's a big loss

Another of Wales' contingent of injured players - British and Irish Lions centre Jonathan Davies - says Webb's absence is a blow but added there is good cover available at scrum-half.

"Obviously it's devastating news for Rhys and Wales and it's a difficult one after Rhys showing what he can do for Wales and the Lions in the last year," said Wales and Lions centre Jonathan Davies.

"He will be a big loss but luckily Gareth Davies has been excellent for us at the Scarlets and he's full of confidence and I'm sure he can do an excellent job for his country."

Davies is one of four Wales players already ruled out of the tournament along with Webb and Lions back-rows Sam Warburton and Dan Lydiate.

Scarlets lock Jake Ball is also likely to miss the whole of the tournament after surgery on a shoulder injury.

First-choice fly-half Dan Biggar is set to miss the first three rounds after injuring a shoulder in last weekend's European Champions Cup loss to Clermont Auvergne.

Fellow fly-half Rhys Priestland is also out of most of the tournament with a hamstring problem and his Bath team-mate Taulupe Faletau has a leg injury.

Back Liam Williams has an abdominal injury and is a doubt for the opening game while wings George North and Hallam Amos, plus Gloucester flanker Ross Moriarty, have only just returned from injury.

Gatland has warned that Williams' injury could require surgery and rule him out of the tournament if it does not respond to treatment.