Jonathan Thomas has told Warren Gatland he is ready to join the Wales squad at the World Cup if Ryan Jones fails to recover from his calf injury.
Coach Gatland is considering calling up a replacement for the 30-year-old back-five forward, who missed Wales' opening defeat by South Africa on Sunday.
Welsh forwards coach Robin McBryde, however, feels Jones has a "realistic chance" of playing in this World Cup.
But Thomas said: "I'm ready. I'm on standby. We'll wait and see."
Jones's calf problem caused him to miss Wales' final two pre-World Cup warm-ups as well as their opening defeat, against the world champions in Wellington.
It is feared the former Wales captain may not recover from his calf problem, which he aggravated in training last week, until Wales' final Pool D game, against Fiji in Hamilton on Sunday 2 October.
"Ryan will continue his rehabilitation with us and is still looking at a return to play time of around two to three weeks," said WRU national medical performance manager Prav Mathema.
The Ospreys forward has yet to feature in a World Cup, having missed the 2007 tournament with a shoulder injury.
Thomas, who played the full 80 minutes in both of the Ospreys' opening Pro12 victories, over European champions Leinster and Edinburgh, is just one of the players on Wales' standby list.
"I've heard there's a few other boys on standby like Gareth Delve and Josh Turnbull," said Thomas.
"I'd love to go but I wouldn't wish injuries upon anyone so let's just hope Ryan gets well soon."
Wales did not suffer any fresh injury problems in their 17-16 defeat to the Springboks on Sunday.
Mathema added: "The fact that we have been able to report no new significant injury concerns to the coaches from the weekend's game means that the decision to allow him [Ryan] to stay and work at getting back to fitness in time for that Fiji match can still stand.
"We have been fortunate on the injury front and come through the South Africa game relatively unscathed with just a few minor bumps and bruises to contend with."
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