01/18/2012 10:29 EST | Updated 03/19/2012 05:12 EDT

Canada's Raonic downs Petzschner to advance to third round at Australian Open

MELBOURNE, Australia - Milos Raonic says he has some work to do if he wants to reach the fourth round of the Australian Open for the second straight year.

Raonic, the 23rd seed in Melbourne, earned a hard-fought 6-4, 5-7, 6-2, 7-5 win over Germany's Philipp Petzschner on Thursday to advance to the third round of the year's first major tournament.

But the win didn't come easy. The 21-year-old from Thornhill, Ont., struggled to close out the second-round win in the same venue where he first began his surge to the top 25 last season.

It's only going to get harder for Raonic in the third round, as he will face either American Andy Roddick or Australian Lleyton Hewitt. The two former No. 1 players meet later Thursday.

"It's really going to be about imposing myself whoever I play, taking care of my serve, looking to try to dictate on the return games when I get the opportunities," Raonic said.

"I'm going to have to work on a few serves tomorrow and also work on the first shots after the return of the serve."

Raonic is off to another strong start this season, starting with a recent victory at an ATP tournament in Chennai, India. But he said that Thursday's match was far form his best effort.

"I didn't serve too well, but I managed to take care of my serve, which is the most important part," Raonic said. "My goal was to make him hit a lot of volleys when he came in. He was doing a good thing there.

"I was struggling a little bit, I don't know why, when I was running forward. He was doing the right thing between making me just play and also putting the pressure on me. He wasn't letting me get into any kind of rhythm on what to expect from him. So that definitely made it tough."

Raonic was frustrated against the 63rd-ranked Petzschner as he tried to serve out the victory leading 5-4 in the fourth set before line call wide drew his ire. He went onto lose the game as Petzschner levelled at the set at five games apiece.

Raonic bounced back to break Petzschner and take a 6-5 lead, then fired an ace to save a break point in the 12th game. He found the empty court with a winner for a match point, but an apparent ace was ruled as a let.

Raonic fought through to finally close it out after nearly three hours when Petzschner hit a forehand long.

Raonic fired 17 aces and 47 winners, but also committed 38 unforced errors. He broke his opponent on five of seven occasions.

In women's play, German Angelique Kerber eliminated Stephanie Dubois of Laval, Que., 7-5, 6-1. Dubois had beaten Russian Elena Vesnina in the first round for only the third Grand Slam singles victory of her career.

"I was aggressive, that was in my game plan," said Dubois, who had to stop playing last September due to a stress fracture in her left foot. "When I was leading in the first set, maybe I went for too much and committed some unforced errors.

"The game at 5-5 was long and could have gone either way. If I'd won it, could have been a different match."

The 97th-ranked Dubois found positives in her game despite the loss.

"I preferred the way I played today rather than my first match," she said. "I'm still looking for confidence after being away form the game for so long.

"Of course I'm not happy when I lose, but it was a positive match for me anyway. (Kerber) was a US Open semi-finalist, so she knows how to play."

Later, Maria Kirilenko of Russia came back in a third set to disappoint Aleksandra Wozniak, from Blainville, Que., 6-4, 1-6, 6-2. Wozniak was in the second round of the Australian Open for the first time in her career.

In doubles, second seeds Daniel Nestor of Toronto and Belarus partner Max Mirnyi began their fortnight with a comfortable 6-2, 6-2 win over young Australians Benjamin Mitchell and Matt Reid.