Gregan (right) said Romania were physically tough

Australia captain George Gregan was pleased with his side's second-half performance after they thrashed Romania in Brisbane.

Gregan watched from the bench, having left the action at half-time with a thigh injury, as his team recorded a convincing 90-8 win.

The injury is expected to keep him out of Australia's next match against Namibia, but is not considered serious.

"Everybody expects you to win by a big score but we had to work hard," Gregan said of the 13-try rout.

"It was a really good game. They are a very physical team and very strong defensively.

"We found it difficult to adjust at the breakdown, and there was a tendency to over-commit.

"Missing our targets allowed them to slip in on the side, but in the second half we played better.

"It was a good start and we can't wait to get to Adelaide."

The hosts will travel south for their next match in Pool A in high spirits despite Gregan's injury.

Match report: Australia 90-8 Romania

The captain's run of 30 consecutive Tests over the last three years will come to an end with Chris Whitaker coming in at scrum-half.

"It's not too serious but probably serious enough to keep him out of next week," Wallaby coach Eddie Jones confirmed.

Jones was delighted by the performance following Australia's scrappy opener against Argentina.

"It's about the performance and I saw more today that was an improvement than in the Argentina match," he said.

"Certainly we dropped some ball, but they were all positive mistakes.

"When you're trying to shift the ball around, you're playing a defense line that plays a little bit different, it can cause handling mistakes.

"I thought the backs sealed the deal for us in the second-half as we scored virtually a point a minute and you can't ask for more than that.

Next time we will play rather than be spectators Romania's Romeo Gontineac

"It was one of those difficult games where everyone expects a cricket score but I would say that the final score was flattering to us."

His Romanian counterpart Bruno Charreyre said that it had not been a fair reflection of his side's capabilities.

"It is asking a lot of a third division national side to take on Ireland eight days ago and then the world champions. Being an amateur team is just not possible to repeat a similarly good performance," Charreyre said.

"I do not think that this type of match is a good advertisement for promoting the sport."