Warren Gatland subjected his Wales players to a brutal review of their defeat to Australia, knowing that a similar performance against South Africa will seal their Rugby World Cup demise.

The injury-ravaged Welsh and Springboks collide in the first quarter-final at Twickenham, with the southern hemisphere giants starting as clear favourites to book a last-four appointment with either New Zealand or France.

Progression as Pool A winners would have been the prize had Wales been able to capitalise on Australia playing with 13-men for seven minites after two players were sin-binned last Saturday.

The Wallabies, who prevailed 15-6, were heroic in defence as they repelled wave after wave of attacks, but Gatland insists Wales’ failings when the whitewash was at their mercy must not be repeated.

“We’ve been pretty critical of the players – Toby Faletau losing ball in contact, Dan Biggar screaming for it with a three on one overlap,” Gatland said.

“We’ve been really hard on the players in terms of making the right decisions at this level.

“You must be able to make decisions under pressure and we didn’t do that on Saturday.

“The players’ reaction was fantastic. We keep saying to them that being critical is about making them better players. We don’t want to make excuses.”

Wales had already confirmed their presence in the quarter-finals by stunning England 28-25 one week earlier and Gatland seized the opportunity to take a swipe at Stuart Lancaster’s men.

“On Monday it was great for players and management to have the opportunity to go to Buckingham Palace,” Gatland said.

“Australia were a bit battered and bruised. I chatted to (Wallabies captain) Stephen Moore and he said ‘tough game on Saturday, a lot tougher than the weekend before (when Australia beat England 33-13)’.”

Gatland insists it was an easy decision to opt for Tyler Morgan ahead of James Hook at outside centre.

Morgan was drafted into the squad last month as a replacement for the injured Cory Allen and will be winning only his third cap, forging a centre partnership with Jamie Roberts.

The 20-year-old has beaten Hook, a player 10 years his senior who has 80 caps, to a place in the starting XV with George North reverting back to the wing.

“Our squad selection has been 100 per cent consistent. We thought Tyler played exceptionally well against Fiji for a young player and he’s an out and out 13,” he said.

Loosehead prop Gethin Jenkins returns at the expense of Paul James and flanker Dan Lydiate is named in the back-row alongside skipper Sam Warburton and number eight Faletau.

Wales registered only their second victory over South Africa last autumn and Gatland insists they must enter Saturday’s last-eight showdown unburdened by fear.

When asked what he was expecting from the Springboks, Gatland said: “Same old, same old.

“They’re an incredibly physical team up front and we have to match them at scrum time and lineout. They have some very strong ball carriers.

“They have got over the shock of being beaten by Japan and that’s galvanised them as a team and as a squad.”