Brumbies centre Tyrone Smith has been drafted into the Wallabies squad after luckless youngster Rob Horne was ruled out of the spring tour with a hamstring tear.

Horne broke down at training in Tokyo on Tuesday and, for the second time this year, was put on a flight home from Japan to Sydney.

The 20-year-old also had his Junior World Cup campaign in Japan prematurely ended because of his chronic hamstring injury.

Wallabies coach Robbie Deans said the entire squad was feeling for Horne, who had been likely to make his senior international debut next Tuesday when Australia's second-string team plays English club side Gloucester.

"He said he was feeling as good as he had and he's been well managed and rehabed and so forth and well warmed up and said he felt great - and then 'bang'," Deans said.

"It's a grade two (tear). He's going home. Tyrone Smith arrives here tomorrow morning."

Smith, 26, joins older brother George, 29, on tour, giving the Wallabies two siblings in the ranks for the first time since Cameron and Andrew Blades represented in the late 1990s.

"We tried to get (Tyrone) into training last week or the week before but he was on his honeymoon in Hawaii," Deans said.

"George volunteered the fact that he had another brother if he was required!"

The younger Smith will almost certainly debut for the Wallabies against Gloucester, when most players involved in Saturday's Test against New Zealand will be rested.

"It's pretty evident the blokes who are going to be starting (against Gloucester) because we don't want players starting in both fixtures, ideally," Deans said.

"So Tyrone, for example, is likely to start.

"Obviously the guys have a pretty clear understanding that they're all going to be involved, that they're all going to get rugby."

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