A tearful Naomi Osaka followed up her Australian Open disappointment with another surprise defeat on Friday when she was beaten 6-0, 6-3 by world number 78 Sara Sorribes Tormo in the Fed Cup.
Spain took an unexpected lead over Japan in the tie in Cartagena after Sorribes Tormo capitalised on a careless performance from Osaka, who made an astonishing 50 unforced errors in the 15 games.
Carla Suarez Navarro then made it 2-0 to the hosts after she eased past Misaki Doi 6-3, 6-4.
Sorribes Tormo enjoyed the backing of a sizeable home crowd at La Manga Club and her consistency proved too much for Osaka, who has never played her best on clay.
"We knew that Sara had the game to make it very uncomfortable for Naomi," Spain captain Anabel Medina Garrigues said. "She stuck to the game plan perfectly."
The winners of the eight qualifying ties will join four automatic entries, holders France, Australia, Czech Republic and hosts Hungary, in the inaugural Fed Cup Finals in Budapest in April.
Osaka, a two-time Grand Slam champion, has endured a shaky start to the year after being knocked out by 15-year-old American sensation Coco Gauff last month in Melbourne, where she had lifted the trophy in 2019.
Since claiming her second consecutive major triumph, Osaka has dipped, failing to go past the fourth round in any of the four Grand Slams since.
The 22-year-old, who has dropped to number 10 in the world, surrendered the first set to Sorribes Tormo in a swift 27 minutes before putting up more of a fight in the second.
But after Osaka led 2-0, Sorribes Tormo came back and a break midway through proved decisive, with a clearly disappointed Osaka struggling to contain her emotions at the finish.
Sorribes Tormo's second career singles win in Fed Cup gave Spain the perfect start, which was extended by Suarez Navarro's comfortable victory over Doi.
Osaka will now have to beat Suarez Navarro in the reverse singles on Saturday to prevent Spain booking their place in the finals in Budapest.
- Serena out-duels Ostapenko -
The United States were well on their way to an appearance in the finals after victories for 23-time Grand Slam winner Serena Williams and newly minted Australian Open champion Sofia Kenin.
Kenin got the ball rolling for the Americans in Everett, Washington, with a 6-2, 6-2 victory over Anastasija Sevastova and Williams followed with a hard-fought 7-6 (7/4), 7-6 (7/3) win over former French Open champion Jelena Ostapenko.
"I was obviously a little nervous coming in after Australia," said Kenin, who needed just 68 minutes to subdue Sevastova. "I felt tired, but I tried to get that out of my mind and just represent and do what I do best."
Williams had a tougher time with Ostapenko, but benefitted from the Latvian's two double faults in the first-set tiebreaker and another double fault to give Williams match point in the second-set decider.
Ostapenko also double-faulted to hand Williams a break for a 6-5 lead in the second set. The US veteran couldn't close out the match however, dropping her own serve and the first two points of the ensuing tiebreaker before storming back with five straight points.
"I'm really proud of being able to get the win for the team," said Williams, who took her perfect record in Fed Cup singles play to 14-0.
Elsewhere, world number five Belinda Bencic thrashed Gabriela Dabrowski 6-1, 6-2 to give Switzerland a commanding 2-0 advantage over Canada, Germany grabbed a 2-0 lead over Brazil and Slovakia took a 2-0 lead over Britain in Bratislava.
The ties between Belgium and Kazakhstan, Romania and Russia, and the Netherlands and Belarus, were all level at 1-1 after the opening day.
Naomi Osaka has had a difficult start to the 2020 season