British number five Watson was defeated 7-6(4) 6-3 by her Spanish opponent and her compatriots Sonay Kartal and Paul Jubb also fell to disappointing results in Melbourne.
Kartal took America's Elizabeth Mandlik to a decider after fighting back in the second set before falling 6-4 3-6 6-1.
Jubb's match against Dalibor Svrcina of the Czech Republic followed a similar pattern after he forced a decider only to ultimately succumb 6-3 1-6 6-4.
Meanwhile, Evans was knocked out of the Adelaide International 2 but his fellow Briton Jack Draper was more successful in his opening match of the tournament.
Evans, the number five seed, was dispatched in straight sets but American opponent Mackenzie McDonald needed tie breaks to advance into the round of 16 after prevailing 7-5 7-5.
British number two Evans was eclipsed by 21-year-old Draper, who dispatched Italy's Lorenzo Sonego 6-4 6-2.
The Adelaide International 2 is the second of consecutive ATP 250 tournaments staged in the city with Novak Djokovic winning the first instalment on Sunday.