Waratahs scrumhalf Brendan McKibbin on Monday departed for the United Kingdom to reinforce the Wallabies squad.

The 27-year-old, who made his Super Rugby debut in 2009 and has appeared at state level for both the Reds and the Waratahs, has been called in to replace his Western Force counterpart Brett Sheehan.

Sheehan had the misfortune to suffer an ankle injury during the first half of Saturday's 22-19 win over Italy at Florence and was unable to complete the match.

McKibbin has appeared in Super Rugby on 30 occasions, with half of those appearances being achieved this year during a campaign which also saw him handle the goal-kicking for much of the competition.

The new player is expected to arrive in Cardiff on Tuesday and will become the fourth replacement to have joined the tour, following on from the Melbourne Rebels trio of Scott Higginbotham, Mitch Inman and Caderyn Neville.

"I woke up to a text message from the Wallabies' manager this [Monday] morning," said McKibbin.

"I was still waking up at 6am [06.00] but it was pretty exciting.  My girlfriend Edwina was over the moon.  I rang my parents too, they're in Queensland so I got them out of bed and gave them some good news to start their week."

Having trained with his NSW teammates at Centennial Park Monday morning, McKibbin says the news is still sinking in.   

"I've spoken to Robbie [Deans] a few times in the past year and I've been through the plays, policies and structure so I'm familiar with things, as much as I can be from the outside anyway.

"It's a bit of a shock to the system that I'll be preparing for a game in a week when I was expecting to be preparing to run up the Coogee stairs and what not!

"That's a bit of a change in mental application but it's pretty full on at the Waratahs at the moment so I feel ready.  There's a really good buzz here, all the guys are working hard.  Michael Cheika has been asking some pretty tough questions of us as a squad, and we've been doing a fair bit of work  mentally and physically.  I'll reflect on that on the flight over there and read up and rest up on the long international flight.  If given the opportunity I'm sure I'll take it with both hands."   

A post-game x-ray later cleared Sheehan of any broken bones, and he has travelled to Wales with the squad ahead of the James Bevan Trophy Test, but will be unable to play a part in the match.

Sheehan will undergo scans in the coming days in Cardiff to determine both the extent of his injury and the course of rehabilitation required.

Waratahs lock Kane Douglas has re-joined the Wallabies squad in Cardiff after missing the Italian leg of the tour in order to stay near his ill mother in London, while he continued rehabilitation from a knee injury.

Douglas will be assessed by the Wallabies medical staff early in the week to determine his availability for the tour's final game.

His return would further bolster the side's second row resources, which took a hit when Rob Simmons was suspended following the tour opening Test in Paris.

The Wallabies' appeal against the eight-game sentence given to Simmons will take place at Bristol on Tuesday.

Australia's final match of 2012 takes place on Saturday, when the Wallabies take on Wales at the Millennium Stadium in Cardiff.