The Ospreys number eight sits out Saturday's final World Cup warm-up game against Argentina in order to rest a troublesome calf muscle.
Jones had been due to skipper Wales for a record-equalling 28th occasion with last season's captain Matthew Rees already out of the World Cup through injury and current leader Sam Warburton being rested.
But Wales coach Warren Gatland will take no chances just four days before he announces a 30-man squad for the tournament in New Zealand.
Gatland has already seen Rees (hooker), centre Gavin Henson (wrist) and wing Morgan Stoddart (broken leg) sidelined from World Cup contention, so 53 times-capped Jones' condition demanded caution.
His absence means Sale Sharks forward Andy Powell gains an 11th-hour chance to press World Cup claims, with Jonathan Thomas joining the replacements and flanker Martyn Williams marking his 99th cap by captaining the team.
"I think I would be worried if Ryan was starting on Saturday," said Gatland.
"The risk of him starting is that potentially it could injure the calf and rule him out of next week's training.
"It is just precautionary. It gives him another week to recover. We are making a sensible decision - we just want to make sure he is right.
"Experience and leadership is also important for us. Ryan is able to cover a few positions in terms of eight, six and in the second row as well.
"A player of that quality, and who has the flexibility in other roles, is important for us.
"He's very disappointed. He wanted to play, but it was about making the decision of him (Jones) having missed out on two other World Cups, why jeopardise anything by playing on Saturday?"
Powell joined Sale from Wasps earlier this summer after being released by the London club following a pub fracas with football fans. He was suspended by Wasps while they investigated the incident.
Last year, Powell was thrown out of Wales' RBS 6 Nations squad after he drove a a golf buggy from the team hotel in the early hours following a victory over Scotland. He was then banned from driving by Cardiff magistrates.
He subsequently rejoined the squad, but suffered an injury in the opening Six Nations game against England last season and has seen Warburton, Dan Lydiate and Toby Faletau form a powerful back-row unit in his absence.
Gatland added: "It is an opportunity for Andy to start on Saturday. I have spoken to Tony Hanks (Sale coach) on a number of occasions, and they've been very impressed with him up there.
"Andy was initially disappointed he wasn't selected for this game. He now gets a chance to start and to show what sort of physical impact he is capable of making."
Wales full-back Lee Byrne, meanwhile, will go into the Argentina game admitting: "The pressure is on."
Byrne's place in the World Cup squad appears to be a formality, but whether or not he starts against opening opponents South Africa in Wellington on September 11 is a subject for debate.
As recently as two years ago, Byrne had no realistic challengers for the Wales number 15 shirt. A Six Nations Grand Slam winner and Test Lion, he reigned supreme.
Gatland, though, now has other options, despite losing two full-back alternatives in Stoddart and Henson.
Rhys Priestland was selected to start as Wales' last line of defence against England at Twickenham two weeks ago before fly-half Stephen Jones pulled out late and Priestland switched positions.
Then James Hook filled the role magnificently in last Saturday's England rematch, scoring a try and kicking two long-range penalties as Wales triumphed 19-9.
And Byrne, now fit again after suffering a knee injury during the Ospreys' final game of last season, has not been oblivious to developments.
"The guys have been doing really well, and it has been about waiting for my chance," he said.
"It was an unfortunate injury to Morgan. He was playing really well and putting pressure on people, and the same with Gavin.
"Rhys Priestland can play 15, James Hook can play 15, so the pressure is on and it is up to me on Saturday to go out there and show what I can do.
"When you first put the jersey on, you are starting from scratch. As far as I am concerned, it's a new season and I am really looking forward to playing again."
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