Welsh battering ram smells blood

Burly Welsh inside centre Jamie Roberts is excited at the prospect of testing out the defensive mettle of Wallabies inside backs James O'Connor and Berrick Barnes this weekend.

Roberts made a huge impression at the World Cup with his bullocking runs from midfield putting his team on the front foot regularly and he made no secret of his intent to impose himself on the relatively lightweight O'Connor and Barnes at the Millenium Stadium this weekend.

"We have made sure this week in defence we are ready to greet him [O'Connor] and Berrick [Barnes] as well," Roberts told AAP.

Barnes shone when he replaced the injured Quade Cooper early in the third-place play-off match between the two sides at the World Cup and he won the man of the match award as the Wallabies claimed the bronze medal.

Roberts has not forgotten that match and is determined to test Barnes' weak shoulder which he injured in the match against the Barbarians last week.

"Berrick had a terrific play-off game against us. Hopefully, we can give him a warm reception," he said.

Barnes is recognised as one of the most solid defenders in Australian rugby and he admitted that he will need to be at his best this weekend if he is to stop the barnstorming Roberts.

"He is a physical player," he said. There are guys that you tackle who are big and imposing blokes. He is hard, he is bones, he is muscle and a hard man to tackle.

"He runs extremely good lines and is a talisman for them and, when he does well, they tend to get momentum off that. It is up to us - whoever, they are big boys. They have speed, too, which is a bit daunting for someone who is only 90kgs as well," added Barnes.