Ryan Jones has been ruled out of the final World Cup warm up match with the Pumas in Cardiff with a calf strain.
The 2005 Lion was due to captain his country for a record-equalling 28th time but Wales coach Warren Gatland has decided not to risk aggravating the injury with the global gathering just over three weeks away.
"I think I would be worried if Ryan was starting on Saturday," said Gatland, who will be without Test Lions Gavin Henson and Matthew Rees in New Zealand.
"We have withdrawn him as a precaution and told him we are happy with what he has done so far in terms of making a claim for RWC selection.
"The 30-man squad will be named at the Millennium Stadium on Monday and, without getting ahead of ourselves, we have told him how important he is to us.
"He's very disappointed. He wanted to play, but it was about making the decision of him having missed out on two other World Cups. Why jeopardize anything by playing on Saturday?"
But while the setback is bad news for Jones, two other Lions are set to benefit from his misfortune.
New Sale signing Andy Powell replaces Jones at No8, while triple Lions tourist Martyn Williams will skipper the side from the openside flank.
The Millennium Stadium encounter now gives Powell, as well as Jonathan Thomas who has been added to the replacements bench, a final chance to push for World Cup selection before Monday's squad announcement.
Powell appears to have fallen behind both Jones and Tongan-born youngster Toby Faletau in the Welsh pecking order and, with Gatland near enough admitting that Jones will be travelling to New Zealand, the 2009 Lion is in need of a big performance on Saturday.
Sam Warburton, Dan Lydiate, Faletau and Jones all appear certainties for Wales' World Cup campaign, leaving Powell and Thomas fighting it out with Williams, Josh Turnbull, Justin Tipuric and Gareth Delve for the remaining one or two back-row slots.