Full-back James Hook, wing Shane Williams and flanker Dan Lydiate are all unlikely to make coach Warren Gatland's starting line-up in Hamilton.
Hook (shoulder) and Lydiate (ankle) were both hurt during last Sunday's punishing Pool D clash against Samoa, while Williams - Wales' record try-scorer with 55 Test touchdowns - has now joined them on the casualty list.
Gatland revealed on arrival in New Plymouth that Williams is nursing a muscle strain at the top of his leg after naming a team showing 11 changes for Monday night's appointment with Namibia at Stadium Taranaki.
"We've had Shane scanned and he has got a little bit of a quad strain, which we think he might have done against South Africa," Gatland said.
"We thought it was a haematoma, which is a knock, and he's played against Samoa. Shane might be a couple of weeks."
Gatland, though, did deliver a positive fitness bulletin on Lydiate, who limped off after just 10 minutes of the Samoa encounter.
"Dan is recovering really well at the moment," he added.
"He is up on his feet doing a bit of jogging around. Hopefully, he's not too far away.
"Dan missed training on Wednesday, and he came to me and asked if I minded. He said he hadn't slept in the last 72 hours. He has been getting up every two hours and icing his leg.
"The initial verdict from the medics was that we were probably going to have to send him home because it was going to be a lot more serious.
"But he has been so professional in the way he has rehabilitated himself. You have to take your hat off to the young man.
"There has been a big improvement in his ankle, and a lot of it is down to him. He is the type of character we want to build in this squad."
Only centre Jonathan Davies, lock Alun-Wyn Jones, skipper Sam Warburton and number eight Toby Faletau remain from the side that defeated Samoa last weekend to face Namibia.
Fly-half Stephen Jones and back-row forward Ryan Jones both return after recovering from calf muscle injuries.
Scarlets playmaker Stephen Jones will win his 101st cap, breaking the Wales appearance record he previously jointly held with Gareth Thomas.
Jones had been poised to achieve that feat against England seven weeks ago, but his calf tightened during the warm-up at Twickenham and has ruled him out of action since.
Former Wales captain Ryan Jones, meanwhile, makes his World Cup debut after missing the 2007 tournament through injury, packing down at blindside flanker alongside back-row colleagues Warburton and Faletau.
There is a first Wales start since last November for Cardiff Blues prop Gethin Jenkins, with full-back Lee Byrne among nine players making full World Cup debuts.
Wales require a bonus-point victory against Namibia and a win against Fiji to keep them on course for a probable quarter-final appointment with Ireland in Wellington next month.
And they will encounter opponents still reeling from an 87-0 drubbing against world champions South Africa just two days ago. It will be Namibia's final game of a tournament that has seen them concede 185 points in three games.
Gatland spoke with Warburton about the prospect of taking a breather, but the captain said: "I want to play every game.
"I've had a few injuries in my career, and this is the best spell I have had so far fitness-wise.
"Warren said to the players you never know which game is your last Test for Wales. Every opportunity I have to play for Wales, I will take it with both hands."
Namibia will exit the World Cup after Monday's game, and for Wales the task is straightforward, but Gatland said: "We are not taking Namibia lightly in any way.
"A lot of thought has gone into this selection looking at potential combinations.
"And we are also giving a few experienced players the opportunity to come back into the side and to stake a claim for selection against Fiji.
"I spoke to the players at training this morning and I said to them it is important that individually and collectively they go out and make a statement on Monday night.
"For those players who take the field on Monday night it is important that they put us coaches and selectors under pressure so they are in contention for the game against Fiji.
"That is only going to be by a good performance. If they don't perform and it is a rusty display, then some of those selections are going to be easier against Fiji."
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