Tennis: Australian Open dark horse del Potro reaches Sydney final

SYDNEY (REUTERS) - Former US Open tennis champion Juan Martin del Potro underlined his status as a dark horse for next week's Australian Open by hammering Dmitry Tursunov to reach the final of the Sydney International on Friday.

The lanky Argentinian, who will be seeded fifth in Melbourne, hit nine aces as he brushed aside the Russian fourth seed 6-4, 6-2 in just over an hour to reach his seventh final in the last 12 months.

Two of those finals were at Masters events in Shanghai and Indian Wells, an indication for some that he might be returning to the level of form that he reached to win the 2009 US Open title before a wrist injury nearly ended his career.

The 25-year-old will meet Australian defending champion Bernard Tomic, who beat Ukrainian qualifier Sergiy Stakhovsky, in Saturday's final at Sydney's Olympic Park.

Del Potro was seeded to meet world No.1 Rafa Nadal in the quarter-finals of the year's first Grand Slam, while Tomic was revealed as the Spanish 13-time Grand Slam champion's opponent in the opening round in Friday's draw.

World No.5 del Potro and Australian veteran Lleyton Hewitt are the only Grand Slam winners apart from Nadal, Roger Federer, Novak Djokovic and Andy Murray still active in men's tennis and the Argentinian believes he might soon be challenging the leading four players again in major finals.

"I think I'm getting closer to the top four guys," he said on court at the end of his match.

"They are still playing such great tennis but if I am fit, I will try to be dangerous for them."

Another former US Open champion, 2011 women's singles winner Sam Stosur, had a less encouraging day, going down 3-6, 2-6 in the semi-finals of the Hobart International to Klara Zakopalova.

Australian Stosur has never been beyond the fourth round at her home Grand Slam and played the Hopman Cup and the Hobart event to try and build some form ahead of the tournament, where she will be seeded 17th.

She received a lesson in taking opportunities from Zakopalova, who converted all five of her break points but saved eight of the 10 the Australian created.

Even worse news for Stosur, who needed a medical time-out because of a nose bleed before the start of the match, is that she was drawn to play the 31-year-old Czech again in the opening round at Melbourne Park on Friday.

At the Auckland Open, American John Isner came from behind to beat Spain's Roberto Bautista 3-6, 7-6 (7-2), 6-4 and set up a final against Chinese Taipei's Lu Yen-hsun, who beat defending champion and top seed David Ferrer of Spain.

Women's world No.9 Angelique Kerber later takes on qualifier Tsvetana Pironkova in the Sydney final.