Rhys Webb ruled out of 2018 Six Nations with knee injury and may have played his last game for Wales

Webb is set to join Toulon at the end of the season which will make him ineligible for the national team

Rhys Webb has been ruled out of the Six Nations with a knee injury (Getty)

Rhys Webb has been ruled out of the entire Six Nations championship after suffering a knee injury in training in a blow that could have ended his Wales career.

The 29-year-old will need “further assessment” on the injury before his recovery period can be determined, but The Independent understands that the British and Irish Lions scrum-half will not play any part in the championship that begins next week, with head coach Warren Gatland calling up uncapped Cardiff Blues No 9 Tomos Williams as a result, joining Scarlets pair Gareth Davies and Aled Davies as the remaining scrum-half options.

A Welsh Rugby Union statement read: “Rhys Webb has been released from the Wales national squad due to a knee injury.

“The injury will restrict Webb's involvement in the campaign and further assessments are required to establish the best course of action.”

With Webb due to move to French side Toulon in the summer – a move that will make him ineligible for selection for the Wales national team – it could potentially be the end of his international career. He will be eligible for this summer’s tour of the United States and Argentina, fitness-depending, as it is part of the 2017/18 calendar.

But Gatland has already stated his intention to use the three Tests against South Africa (in Washington) and Argentina as chances to develop squad depth and play fringe players, with his attentions very firmly on the 2019 Rugby World Cup, meaning that Webb is an unlikely candidate to be included for the tour.

Should he miss out on selection, Webb will be ineligible for Wales until he joins one of the four Welsh regions as the 31-cap scrum-half is a long way short of the 60-cap threshold that would omit him from the selection policy, and should he honour his full Toulon deal that runs until 2021, he would be 32 years old before the chance to return becomes available.

The news is another devastating blow to Wales’ hopes of competing for the Six Nations title, and comes just one day after Gatland claimed that he expects his side to win the championship, despite the growing number of injuries on his hands.

Webb is unlikely to play for Wales again due to his summer move to Toulon (Getty)

Webb joins a long list of high-profile players in key positions that will miss part or all of the tournament, with British and Irish Lions captain Sam Warburton already ruled out for the rest of the season after undergoing knee surgery. Centre Jonathan Davies is also sidelined for the rest of the year following an operation on his foot.

First-choice No 8 Taulupe Faletau is in a race to be fit if he is to play any part in the Six Nations after suffering a knee injury in December while playing for Bath, while fly-half Dan Biggar has been ruled out of the first three rounds against Scotland, England and Ireland due to a shoulder injury that he suffered in the Ospreys’ European Champions Cup defeat by Clermont Auvergne. Rhys Priestland, Biggar’s likely replacement, is already unlikely to feature at all due to a hamstring injury.

Uncapped Cardiff scrum-half Tomos Williams has been called up to the squad (Getty)

Gatland also faces a nervous wait over the fitness of Liam Williams, with the full-back suffering a recurrence of an abdominal injury on his return from a two-month lay-off two weeks ago. The 26-year-old is a doubt for the opening Six Nations game against Scotland, and could yet miss the entire tournament as he needs surgery on the injury. Speaking at the Six Nations launch on Wednesday, Gatland left it in no doubt as to who was to blame.

“It's probably an injury that six weeks ago he should have had an operation on it, but Saracens had rehabbed him and he's come away from the game against the Ospreys feeling very sore," said Gatland.

"Potentially he had the option of having surgery before but that wasn't taken. Our medical team had a look and want to rehab him extensively over next couple of weeks."