Lions Tour:Wales captain Ryan Jones has been called up to join the British and Irish Lions Tour in South Africa and will replace stricken Ireland flanker Stephen Ferris, who will miss the remainder of the 10-match trip.

Grand Slam winner Ferris, a strong candidate to clinch a Lions Test place against world champions South Africa on Saturday week, has suffered a knee ligament tear that means he faces a six-week lay-off.

Jones, who joined the 2005 Lions tour in New Zealand as a replacement and ended up playing in the Test series, will link up with the squad in Cape Town tomorrow.

Ferris twisted his right knee during a training drill, and a scan subsequently revealed the injury's full extent.

Lions head coach Ian McGeechan said: "He had the scan on Tuesday morning that showed he had a grade two tear to his medial collateral ligament.

"This usually requires a four to six-week recovery period and is severe enough to mean he will miss the rest of the tour.

"Therefore, with six matches left on tour after Wednesday's match against the Sharks, we believe we need to fly out a replacement as cover for the backrow.

"Ryan is on the stand-by reserve list and has been playing for Wales over the last few weeks in the USA and Canada.

"He will fit right in as he knows a lot of the players and he was a Lions replacement on the 2005 tour to New Zealand.

"In fact, on that tour he showed how competitive he is as an individual by forcing his way into the Test side for all three matches against the All Blacks."

Ulster forward Ferris made a powerful start in South Africa, scoring tries in each of his two appearances against the Golden Lions and the Cheetahs.

And such was his impact he looked set for an intriguing head-to-head for the Lions Test number six shirt with England's Tom Croft.

Ferris' dream though, is now over, as he joins a list of players who have fallen by the wayside.

McGeechan saw hooker Jerry Flannery, scrumhalf Tomas O'Leary and Tom Shanklin all fail to make last month's flight to Johannesburg due to injuries, while a 12-week suspension sidelined Munster flanker Alan Quinlan.

For Jones, the call-up comes at the end of what has been a testing season.

He led Wales to the RBS 6 Nations title and Grand Slam last year, but has failed to recapture his form since then.

He was one of three Six Nations skippers who originally failed to gain selection for the Lions trip, being joined by Scotland's Mike Blair and England's Steve Borthwick.

Blair, however, was summoned as replacement for O'Leary, and Jones will now look to make his mark in his probable tour debut against the Southern Kings in Port Elizabeth next Tuesday.

The Lions, meanwhile, can now only hope Wales wing Leigh Halfpenny does not follow Ferris out of the tour.

Halfpenny has aggravated a thigh injury that delayed his arrival in South Africa until last week, and was due to undergo a scan as the medical team made a full assessment.

With the selection race gathering pace towards next week's first Springboks encounter, several players will need to make an impression on McGeechan.

And that list probably includes Wales speedster Shane Williams, the 2008 world player of the year whose tour has yet to take off.

Williams' Ospreys team-mate Tommy Bowe and Harlequins' Ugo Monye are current favourites for the Test wing slots, although Williams - especially given his dynamic try-scoring prowess - cannot be discounted.

He is back in action only five days after conceding an interception score to Cheetahs centre Corne Uys - and the pressure is on.

"I expect Shane to continue to defend the way he has been on this trip. He has stepped up to the plate, defensively," added Edwards.

"I've said to him that players like him who are touching the ball and playing right in the faces of the defence, at certain times are going to get passes picked off.

"He has to continue to do that, don't be scared and don't go back on the wing, hoping the game passes by.

"He has got to continue to force himself on to the game. In training yesterday he had a real spring in his step and I am really looking forward to him playing."

The Lions will tackle a Sharks team shorn of Test stars like John Smit, JP Pietersen, Ruan Pienaar and Adi Jacobs, who are currently in camp with the Springboks.

And, while the Lions can still expect a fierce battle from South Africa's second-ranked Super 14 side - their line-up features Springboks such as Deon Carstens, Johann Muller and Jannie du Plessis - Sharks coach John Plumtree believes the absence of so many top names is unfortunate.

"Personally, I think the (South African) provinces should be at full strength," said former Swansea boss Plumtree, who coached Wellington against the 2005 Lions.

"A tour like this is unique and there should be less emphasis on just winning Test matches, more a celebration of rugby.

"It's a pity we don't have a full-strength Sharks.

If the Lions are to make it four wins out of four - they've never lost in 10 previous meetings stretching back 99 years - then breakdown supremacy and vastly-reduced turnovers will be vital.

"The breakdown and what goes on at the ruck in terms of quick ball is the most important part of the game," admitted Lions skipper Paul O'Connell.

"We've been working on it and we will continue to work on it right up until the end of the tour.

"With three games to go, we are halfway through the build-up before the first Test and probably places are still up for grabs.

"The more I think the squad believes that and the more it continues that way, the happier the squad will be."

Jones said of his call-up: "I am just really looking forward to joining the squad later this week.

"It is disappointing for Stephen Ferris who is a superb player, and I wish him a quick and full recovery from his injury.

"I am anxious to help the Lions in any way I can, and I recognise how this is a great honour."