But veteran centre Matt Giteau is adamant they can handle any "stress" thrown their way in the coming weeks after delivering their best performance of the tournament.

The Wallabies sent a warning to their rivals with a brilliant 33-13 win against England on Saturday night (Sunday morning AEDT) that doubled as a fatal blow to the hosts' campaign.

Horne injured his shoulder in the 10th minute and will have scans to see if his tournament is over while Israel Folau rolled his ankle and Giteau was hit with a behind-the-play crunching Owen Farrell tackle that left him with a sternum problem.

Folau and Giteau are expected to stay on but winger Horne's fate rests with his recovery and whether there is any major damage to his shoulder joint.

If he is ruled out, ACT Brumbies playmaker Christian Lealiifano looms as a likely replacement if needed while coach Michael Cheika could also opt for another winger which would see Nick Cummins enter the frame.

The Wallabies were hit with their first injury blow last week when Will Skelton (pectoral) and Wycliff Palu (hamstring) were forced to return to Australia.

Giteau said the Wallabies would avoid getting carried away with the hype of their win against England, despite some section of the UK media declaring "we may have just seen the World Cup winners, and it's not England".

"The most pleasing part was there was a period where we were under a lot of stress in the second half probably between the 55th to the 70th minute, they were coming with a bit of a wet sail," Giteau said.

"It's easy to give in at times, but we stayed tough in those hard moments and as a team I think we showed a lot of character.

"It can possibly kickstart things ... but for us there's a lot of footy to go so we're not getting carried away.

"When you get [a clear understanding of your roles], even if you've got injuries, you can shoulder it."

Farrell was sent to the sin bin for his hit on Giteau, which left the 98-Test star writhing in pain on the ground.

It was a game-changing moment and Bernard Foley's penalty goal after the late tackle ended England's hopes of mounting a late comeback.

But Giteau recovered to put the icing on the cake with a last-minute try which hammered the final nail into England's coffin.

Giteau was unsure of how serious his injury was. "I'll have a look at it tomorrow, I'm pretty sore at the moment. We'll wait and see what happens.

"It's a tough competition, I'm sure there are a lot of teams who are hurting and have injuries, little niggles. But it's the team that can handle those the best and stay fit."

The Wallabies' win sets up a huge match against Wales on Saturday (Sunday morning AEDT), with the winner to finish at the top of the pool of death.

Wallabies coach Michael Cheika is preparing for a showdown with the "mastercoach" Warren Gatland, who led the British and Irish Lions to a series win against Australia in 2013.

But Wales has lost its past 10 matches against Australia.

"This whole journey is about ourselves, we've still got a lot to do and we come up against the mastercoach [Wales mentor Warren Gatland] next week," Cheika said.

"We've got to stay real, be humble and get on to the next day preparation and get better.

"You've got to keep the crowd out of the game [at Twickenham], it's like a tsunami."

Giteau will play his 100th Test in the quarter final. It's a moment he thought may never come after he was axed from the 2011 World Cup squad and moved his career to France the same year.

The 33-year-old is the only Wallaby left who was part of the 2003 final and the 2007 quarter final defeat at the hands of England in World Cups.

"But it was never about that ... it was a game in isolation. For us, we need to review that game and review it hard because it wasn't perfect," Giteau said.

"It's just important for us to build moment [against Wales]. The focus is to get better, not where we finish. We need to get better as a team and if you do that, you'll play finals footy and go deeper into the tournament."