Chan Yung-jan earned one of the biggest upsets of her career as the qualifier outlasted former world No.1 Jelena Jankovic to reach the semi-finals of the WTA tournament in Carlsbad, California on Friday.

Taiwan’s Chan, who is ranked 161 in the world, dealt a blow to the third seeded Jankovic’s hopes as she won 6-7 (4-7) 7-6 (10-8) 7-5 – the second longest match of the season on the WTA Tour.

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 unravel 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.

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.