Annika Beck fought back to beat Eugenie Bouchard in three sets to reach the second round of the BNP Paribas Open in Indian Wells.
Germany's Beck lost the first set but rallied to secure a 3-6 6-2 6-2 win over the 2014 French Open semi-finalist Bouchard.
Spanish qualifier Sara Sorribes Tormo sailed past Ekaterina Makarova to secure a shock second-round spot at Indian Wells.
Makarova, a semi-finalist at the Australian Open as recently as 2015, fell 6-4 6-2 the 20-year-old.
Japan's Naomi Osaka overcame compatriot Risa Ozaki 6-4 6-2 while Katerina Siniakova survived a scare to beat world No.98 Mona Barthel of Germany.
Czech Republic's Lucie Safarova was a comfortable 6-3 6-2 winner against Spain's Lara Arruabarrena and Jelena Jankovic beat Irina Falconi 6-2 3-6 6-3.
Shelby Rogers emerged as a 6-4 7-6 (7-4) winner in the all-American clash against Jennifer Brady while their compatriot Varvara Lepchenko beat Yaroslava Shvedova 4-6 6-2 6-4.
Another American, Lauren Davis, took almost three hours to triumph 6-4 4-6 7-5 against Viktorija Golubic.
In other first-round matches, Mariana Duque-Marino beat Patricia Maria 6-4 0-6 6-4, Magda Linette saw off Taylor Townsend 6-4 6-2 and Julia Goerges triumphed 7-5 6-2 against Ajla Tomljanovic.
There was a surprise win for Shuai Peng over Lesia Tsurenko while Donna Vekic also upset the odds in beating Alison Riske.
Pauline Parmentier progressed while Andrea Petkovic benefited from Vania King's retirement to set up a second-round clash with second seed Angelique Kerber.
