* Pironkova stuns Kerber for first title
* Del Potro sets up Tomic final in Sydney
* Ferrer falls short in Auckland (Updates with later matches)
FRSYDNEY, Jan 10 (Reuters) - Bulgarian qualifier Tsvetana Pironkova's fairytale run at the Sydney International ended with her first WTA title when she stunned world number nine Angelique Kerber 6-4 6-4 in the final on Friday.
Pironkova had already beaten world number six Petra Kvitova and number seven Sara Errani in the seven matches it took her to get the final and rode a second set fightback from her German opponent to claim the victory.
"Mum and Dad, we have a trophy," the 26-year-old former Wimbledon semi-finalist beamed after her triumph.
Juan Martin Del Potro earlier underlined his status as a dark horse for next week's Australian Open by hammering Dmitry Tursunov to set up a men's final against Bernard Tomic.
Men's world number three David Ferrer was also the victim of a shock, however, when his bid for a fifth Auckland Open title was ended in the semi-finals by a 6-4 7-6 (7-4) loss to Taiwan's Lu Yen-hsun.
At the Kooyong Classic exhibition, France's Gilles Simon turned his ankle badly and was forced to retire while trailing compatriot Richard Gasquet 7-6 (7-3) 1-0.
Simon will have scans on the injury but his participation in the Australian Open, where he is seeded 18th, must be in serious doubt.
Tall Argentine Del Potro, who will be seeded fifth in Melbourne, hit nine aces as he brushed aside Tursunov 6-4 6-2 in just over an hour to reach his seventh final in the last 12 months.
Two of those were at Masters events in Shanghai and Indian Wells, an indication for some that Del Potro might be returning to the level of form he reached to win the 2009 U.S. Open title before a wrist injury nearly ended his career.
In Saturday's final, the 25-year-old will meet Australian defending champion Tomic, who made heavy work of coming from behind to beat Ukrainian qualifier Sergiy Stakhovsky 6-7 (4-7) 7-5 6-3.
Del Potro is seeded to meet world number one Rafa Nadal in the quarter-finals of the year's first grand slam, while Tomic was revealed as the Spanish 13-times grand slam champion's opponent in the opening round in Friday's draw.
World number five Del Potro is one of only six active male grand slam champions and the Argentine believes he might soon be challenging Nadal, Roger Federer, Novak Djokovic and Andy Murray again.
"I think I'm getting closer to the top four guys," he said on court. "They are still playing such great tennis but if I am fit, I will try to be dangerous for them."
Sam Stosur, another former U.S. Open champion, went down 6-3 6-2 in the semi-finals of the Hobart International to Klara Zakopalova, who she will meet again in the first round at Melbourne Park.
Zakopalova will first face Spain's Garbine Muguruza Blanco in the Hobart final after she thrashed compatriot Estrella Cabeza Candela 6-0 6-1 in the second semi-final.
At the Auckland Open, world number 62 Lu stunned Ferrer in two sets to bring the Spaniard's 14-match, three-year winning streak at the tournament to an end.
Lu will face big-serving American John Isner, who came from behind to beat Spain's Roberto Bautista 3-6 7-6 (7-2) 6-4, in his first ATP final on Saturday. (Editing by John O'Brien)