Warren Gatland has already lost prop Aaron Jarvis (knee ligaments) and lock Bradley Davies (severe concussion) after they were injured during a 33-10 loss to world champions New Zealand three days ago.
Elsewhere, centre Jamie Roberts (hip) will not train during the early part of this week, while flanker Ryan Jones has stitches in a head wound and will also only do limited training.
Wing George North (hip) remains in contention to return in next Saturday's Millennium Stadium clash against Australia after missing the All Blacks game, lock Ian Evans (knee) has been scheduled to undergo a fitness test and fly-half Dan Biggar is in limited training following a shoulder problem.
Bath prop Paul James and Perpignan utility back James Hook have returned to their clubs, meanwhile, as the Australia match falls outside the International Rugby Board's autumn Test window, but France-based trio Mike Phillips, Gethin Jenkins and Luke Charteris have remained with Wales.
Gatland has put back his scheduled team announcement until Thursday lunchtime.
"The injuries during this autumn campaign have challenged our strength in depth in many areas," Howley said.
"But further down the line I am sure we will look back and see this time has been used as development for players.
"Australia are a superb side. They are very talented, and they are very effective at set-piece - I thought their scrum went particularly well against England at Twickenham.
"I think the way you put southern hemisphere sides under pressure is to be very good in the contact area, keep ball and go through the phases."
Howley, meanwhile, has rounded on New Zealand forward Andrew Hore, condemning his behaviour as "an absolute disgrace" following the incident that sidelined Davies.
While Davies continues his recovery, All Blacks hooker Hore must prepare for a disciplinary hearing tomorrow that should see him land a lengthy ban after being cited by match commissioner Mike Rafter for striking an opponent.
"What Hore did has got no place on a rugby field as far as I am concerned," former Wales captain Howley added.
"It was an absolute disgrace. He has been cited, and I am sure it won't be taken too lightly.
"Situations and incidents like that have no place on the rugby field, and it had a huge impact on the game.
"It is not what the All Blacks do. They are a good enough team, anyway, so we are very, very surprised by the actions of the player."
Defeat for Wales against Australia would see them lose a place among the world's top-eight teams ahead of next Monday's 2015 World Cup pool draw, dropping them into tier three and a potentially punishing group.
If they win or draw, though, Wales will stay seventh.
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