But giant lock Will Skelton is still a work in progress with coach Michael Cheika saying the 140-kilogram monster will be eased into international rugby.

New Wallabies coach Cheika said Horwill was the quickest of all forwards to adapt to the team's new playing style for the spring tour of Europe.

It's a timely boost for Horwill ahead of the Test against Wales in Cardiff and comes a year to the day after Ewen McKenzie made the shock decision to strip him of the captaincy and replace him with Ben Mowen.

All players are getting a fresh start under Cheika, however,  with starting XV spots up for grabs for the Test against Wales on Sunday morning.

Horwill has been linked to a rich deal with English club Harlequins and the 56-cap veteran is in a tussle with Rob Simmons, Sam Carter and Skelton for Test game time.

"A few guys stepped up [in the win against the Barbarians] … I thought James Horwill had a really good work rate," Cheika said.

"He probably understood the new system in the forward pack the best and by consequence he was able to get a really high work rate.

"I think there are a few opportunities for guys to push themselves into space."

Back-rower Scott Higginbotham has been ruled out of the clash in Cardiff, but will stay with the team until the severity of his hamstring injury is known.

Rookie Sean McMahon and Western Force captain Matt Hodgson are competing to replace Higginbotham in the starting side.

Horwill was relegated down the lock pecking order during McKenzie's tenure as Wallabies coach, despite the pair guiding Queensland to a Super Rugby title in 2011.

But Cheika wants big, physical forwards and Horwill's efforts in the 40-36 win against the Barbarians have put him in contention for a starting berth against Wales.

Simmons was rested against the Barbarians and it is likely he will be given the chance to play against Wales.

Cheika is likely to stick with the majority of the team which played against New Zealand three weeks ago, believing they deserve another opportunity.

Horwill will battle with Carter and Skelton for the remaining starting second-row spot and a place on the bench.

NSW powerhouse Skelton is still developing and Cheika's plan is to increase his game time and fitness in Super Rugby next year, but the coach said: "I'm more than confident of him playing in games, he can have an impact without a doubt.

"I'd like [the second-rowers] to all play a bit better to push for competition, there's no doubt about that. It's about picking a combination that can do the job for us."

The Reds and ARU are hopeful they can keep Horwill beyond the World Cup next year, but speculation suggests he has already committed to a rich deal with Harlequins.

Carter injured his ankle in his Test debut in June, but joined Simmons as the first-choice lock pairing for the Rugby Championship.

The 25-year-old is in Europe for the first time and is hopeful of retaining his Test jersey.

"We've only had three or four training sessions together, we're slowly building and hopefully we can create a style we can all get on with," Carter said.

"I'm going to have to up my game in a lot of different ways but aggression is something I'm definitely focusing on. I've got to take the opportunities that come."