CARLSBAD: Chan Yung-jan earned one of the biggest upsets of her career as the qualifier outlasted former world No. 1 Jelena Jankovic 6-7 (4/7), 7-6 (10/8), 7-5 to reach the semi-finals of the WTA Carlsbad event.

Taiwan's Chan, who is ranked 161 in the world, dealt a blow to the third seeded Janokovic's hopes as she won the second longest match of the season on the WTA Tour on Friday. The encounter lasted three hours, 13 minutes -- four minutes less than the longest so far on the circuit.

Chan was playing in her ninth career quarter-final -- her last was three years ago -- and made the most of the opportunity against the Serb.

Chan moves on to face French top seed Marion Bartoli or American fifth seed Christina McHale in the semis.

Jankovic, who has a home in the area, was up a set and led 3-1 in the second when she appeared to come unravelled after Chan took a medical timeout.

A broken string on the final point did not help her cause and provided a fitting punctuation to the disappointing end.

"I'm frustrated and disappointed," said Jankovic. "I completely lost focus. It was so tough mentally and physically and my forehand let me down.

"I had the match under control and let it go. I let her come back, I messed up. When you're down you have to keep the focus."

Chan will be in not so familiar territory when she plays only the fourth WTA level semi-final of her career. Her last came in 2008 in Strasbourg.

Chan dropped the opening set in a tiebreaker and saved a Jankovic match point in the second before levelling on her own first set point.

In the third, the challenger ran out a 5-2 lead only to see the 19th-ranked Jankovic, who finished world number one in 2008, catch her and force another tiebreak.

The Serb saved one Chan match point with a forehand winner to the corner before sending a return long as she played with two strings gone.

"There was a 99 per cent chance for her to win on that point and a one per cent chance for me," said Jankovic.

"If she just kept playing it would only be a matter of time before I made a mistake with that broken string."

Jankovic has been on a slow road back to form over the past few seasons and had played in her first final last month in Birmingham since Cincinnati last summer.

Prior to this week, the Serb had lost in the first round 11 times this season.

In a quick match lasting half the time of the Jankovic struggle, second seed Dominika Cibulkova beat Poland's Ursula Radwanska 6-4, 6-4. AGENCIES