Eugenie Bouchard's woes continued at the Monterrey Open after she was eliminated in the first round, but three-time champion Anastasia Pavlyuchenkova advanced.
Canadian Bouchard was a shock casualty on Monday, ousted by Sara Sorribes Tormo 7-6 (10-8) 6-3 as she looks to win her first match since the Australian Open in January.
It was a case of missed opportunities for Bouchard, who only converted three of 17 break point chances on the Mexican hard courts.
Bouchard - a Wimbledon runner-up in 2014 as well as semi-finalist at the Australian and French Opens in the same year - a now has a win-loss record of 5-7 having struggled at Acapulco, Indian Wells, Miami and Monterrey.
There was no such trouble for second seed Pavlyuchenkova in her quest for a fourth Monterrey title.
Russian Pavlyuchenkova eased past Tatjana Maria 6-1 6-3 in the opening round.
Caroline Garcia - the French third seed - also progressed to the next round with a 4-6 6-2 6-3 victory over wildcard Renata Zarazua.
Donna Vekic accounted for Patricia Maria Tig 6-4 6-1, Julia Boserup defeated Nao Hibino 6-0 6-2, while Catherine Bellis lost 7-6 (9-7) 6-4 to Naomi Broady.