Maria Sharapova's bid for a second title in as many weeks ended abruptly on Tuesday with a loss to eighth-seeded Magdalena Rybarikova in the opening round of the Kremlin Cup in Moscow.
Rybarikova overcame a partisan crowd and benefited from 46 unforced errors by her Russian foe to secure a 7-6(3), 6-4 victory.
The Slovak won the last five points of the opening set tiebreaker before breaking Sharapova for the first time in the second set to end the match in one hour, 55 minutes.
"It was very difficult for me, because it felt like Fed Cup. It's absolutely normal, Maria is a huge superstar here and she's a real champion," Rybarikova said. "I'm happy that I went through this match, and it's good for my confidence. I'm very happy with that."
Sharapova ended a 29-month title drought on Sunday by winning the Tianjin Open. The five-time Grand Slam champion had not won a tournament since beating Carla Suarez Navarro in the 2015 Italian Open in Rome, several months prior to her 15-month suspension for using the banned drug meldonium.
Darya Kasatkina recorded the upset of the day after notching four aces en route to a 7-6(2), 6-1 win over fellow Russian and fifth-seeded Anastasia Pavlyuchenkova. Pavlyuchenkova was the 2014 champion and 2015 finalist in Moscow and was coming off a long week at the Prudential Hong Kong Tennis Open.
Seventh-seeded German Julia Goerges had a much easier time of it on Tuesday, recording seven aces to coast to a 6-0, 6-3 win over Russian qualifier Polina Monova in one hour, 15 minutes. The resounding win set up a second-round meeting with Yulia Putintseva of Kazakhstan.
Russian Natalia Vikhlyantseva and Belarus' Vera Lapko breezed to straight-set wins Tuesday while Romanian Irina-Camelia Begu posted a 6-1, 3-6, 6-3 victory over Russian Elena Rybakina.