And Wallabies coach Michael Cheika wants Horne's desperation to rub off on the rest of the squad as they chase their international dreams at Twickenham.

But while Horne is making a fast recovery, there are more doubts over Israel Folau (ankle) and David Pocock (calf) after both sat out an intense training session on Wednesday (Thursday morning AEDT).

In a week where Matt Giteau and Stephen Moore play their 100th Tests to add motivation for the players, it's Horne's appearance at a physical training session which boosted the Wallabies.

Horne's tournament was all but over when he suffered a partial shoulder dislocation when he scrambled to make a tackle in the opening 10 minutes against England two weeks ago.

But such is his value to the team, Cheika gave him an extended time to prove his fitness and Horne was the surprise man at Wallabies training in Teddington.

Even if he is unable to play against Scotland, Cheika wants to keep him in the squad if the progress to the semi-finals.

"He's back in training, we're trying to see if he'll be available for this week's game," Cheika said.

"He got into some contact (on Wednesday) and said he felt good, which is very positive because we probably didn't think he would.

"He'll jump in again on Friday and we'll make a decision from there.

"Rob Horne is desperate to be selected, and he's prepared to go through the pain to do it. I think if he's not right this week he will definitely be right going further."

Folau is expected to start at fullback against Scotland but is being given a light training week to avoid more damage to his ankle.

Pocock has been cleared of a tear in his calf muscle, but the Wallabies coaching staff are treading carefully with his return to the field.

Kurtley Beale and Ben McCalman loom as the likely men to step in if they are unable to take their places.

Drew Mitchell is expected to hold on to his wing spot, but Horne's presence was a welcome sight after coaching staff feared his tournament was over after the match against England.

The Wallabies have already had to send Wycliff Palu (hamstring) and Will Skelton (pectoral) home after they suffered injuries.

But Horne has stayed on and Cheika says his determination indicated the desperation to be a part of the Wallabies' World Cup bid.

"That's what it says about him. I think the players on our trip this year, it's been really interesting. Wycliff Palu stayed and played through an injury to do his bit for the team. (Will) Skelton was desperate to stay even though his pec was ripped off the bone.

"Now anyone that has had any type of niggle, they're making sure that no one knows about it so they can stay."