Sam Stosur and Chinese partner Zhang Shuai have lost their opening match at the WTA Finals in Guadalajara.
Fourth-seeded combination Nicole Melichar-Martinez and Demi Schuurs proved too strong today, recording a 6-2 6-2 victory.
The American-Dutch team were clutch under pressure, saving nine of the 10 break points they faced in the 62-minute match.
It snaps an 11-match winning streak for the fifth-seeded Stosur and Zhang, which included their title-winning runs at Cincinnati and the US Open.
This was Stosur and Zhang’s first match together since their Grand Slam-winning run in New York and they struggled to replicate that form, committing 17 unforced errors compared to their opponent’s eight.
Stosur is a two-time champion at the prestigious season-ending championships, having captured the 2005 and 2006 titles alongside American Lisa Raymond.
The 37-year-old’s bid to win a third title is still alive, with two more round-robin matches to play this week. The top two performing teams from their group advance to the semifinals.
Aussies in action – WTA Finals
 Nicole Melichar-Martinez (USA)/Demi Schuurs (NED) d  Sam Stosur (AUS)/Zhang Shuai (CHN) 6-2 6-2
 Sam Stosur (AUS)/Zhang Shuai (CHN) v  Shuko Aoyama (JPN)/Ena Shibahara (JPN)
 Sam Stosur (AUS)/Zhang Shuai (CHN) v  Darija Jurak (CRO)/Andreja Klepac (SLO)