Toronto, 10 August 2011 | AAP

Jelena Dokic’s preparation for the US Open has suffered a setback with the 2000 Wimbledon semi-finalist forced to retire in the opening round of the Rogers Cup in Toronto.

Dokic’s match against Serbian qualifier Bojana Jovanovski lasted just 9 minutes and 20 seconds.

The premature exit follows two consecutive first round hardcourt losses for Dokic, who was beaten 6-1 4-6 7-5 by Japan’s Ayumi Morita in San Diego after being downed 6-3 6-4 by China’s Zhang Shuai in Washington.

Dokic’s US struggles came after she returned from a short injury lay-off following this year’s first round loss at Wimbledon.

Dokic had pulled out of two events in July prior to the WTA hardcourt event in Washington due to a hamstring injury.

The nature and severity of Dokic’s current ailment remains unclear at this stage.