Defending champion Roddick rolls on at Brisbane

Defending champion Andy Roddick weathered an early onslaught from hard-hitting Ukrainian Alexandr Dolgopolov before steamrolling him 6-4, 6-1 to book a quarter-final place at the Brisbane International on Wednesday.

The 22-year-old Dolgopolov was the early aggressor, attacking Roddick's serve to win an early break and go up 4-2.

The American world number eight quickly broke back, however, and reeled off 10 of the final 11 games to seal the match in less than an hour.

"I knew that he was aggressive to the point of psychosis, he said.

"He came out in the first six games and I didn't really do much wrong," he added.

"When someone is going to try and hit a winner from whatever ball they get on the very first shot, and if they convert, there's very little you can do.

"It was my plan to make him come up with those shots for the better part of a couple of hours and it caught up to him a little bit," he added.

Roddick rocketed down 15 aces in the match to raise A$1,500 ($1,508) in donations for victims of devastating floods in northern Queensland state that have affected 200,000 people across an area larger than France and Germany combined.

"It's a very small part what we're doing here. It was Sam Stosur's idea," said the 2003 US Open champion, who joined the Australian women's world number six in pledging A$100 per ace.

The second-seeded Roddick defeated Czech Radek Stepanek in the final last year on the way to a quarter-final appearance at the Australian Open.