Jonathan Humphreys admits that Wales’ mood after topping their Rugby World Cup group with an unbeaten record has been tempered by injuries to Taulupe Faletau and Gareth Anscombe.
Number eight Faletau, who suffered a broken arm during Wales’ 43-19 victory over Georgia, is out of the tournament.
Fly-half Anscombe, meanwhile, withdrew 45 minutes before kick-off in Nantes due to a groin injury.
And full-back Liam Williams was on crutches after the Georgia game following a blow to his knee, but while he could miss training in the early part of this week Wales are hopeful about his quarter-final prospects.
“It is a big loss, he is a true world-class player,” Wales assistant coach and forwards specialist Humphreys said, of Faletau.
“He is great around the place, but in a tournament these things happen and we have been very lucky in terms of the amount of injuries that we’ve had.
“You can’t replace what Toby (Faletau) gives, in terms of his intelligence and what he does, how he always turns up at the right place and makes the right decision at the right time.
“There is a huge onus now on everybody else to bring more.
“We are delighted that we topped the group, but then when you have close members of the squad who have been injured you are clearly down about that. It affects the mood.
“It is a tough one for Toby, but hopefully Gareth won’t be too long. He felt something in the warm-up and (we) made the decision not to play him. We will know over the next 36 hours what his chances are.”
If Wainwright moves positions, the vacancy at blindside flanker could mean a recall for seasoned campaigner Dan Lydiate, while Exeter’s Christ Tshiunza is also an option, along with switching captain Jac Morgan from openside and handing Tommy Reffell the number seven shirt.
Humphreys added: “We are blessed with the options that we have, but it still doesn’t detract from fact that Toby has been a massive player for us. Whoever steps in I am sure will step up to the plate.
“I think Aaron has been exceptional, and I and he know there is more in him.”
Anscombe’s injury meant a late call to the starting line-up for Sam Costelow, while Dan Biggar is continuing his recovery from a pectoral muscle strain and should feature in Marseille.
“Those senior boys talking to me, just telling me to do my job and to relax, that was massive for me, especially as a young 10. I am just glad we got the job done.
“You can never switch off, especially in this pressured environment. You have got to be ready at all stages. I did my homework, I knew the role and luckily it went well.”