Eugenie Bouchard's comeback from the concussion she suffered at the U.S. Open was stalled by a 6-4, 6-4 loss to Hungary's Timea Babos at the Shenzhen Open in China on Thursday.
This week, Bouchard won her first match on tour since slipping and falling in the locker room at the U.S. Open in September and hitting her head.
The sixth-seeded Canadian then reached her first quarter-final in nearly a year by beating Nicole Gibbs in the second round of the Shenzhen Open — one of several tournaments this week where players are prepping for the upcoming Australian Open.
Against Babos, however, Bouchard connected on just 58 per cent of her first serves, and failed to convert five break points.
In other matches, top-seeded Agnieszka Radwanska advanced to the semifinals with a 6-3, 6-2 win over China's Wang Qiang, and Alison Riske of the United States beat Anett Kontaveit of Estonia 6-1, 3-6, 6-3.
Raonic wins season debut in Brisbane
Canada's Milos Raonic, back in action for the first time this season, defeated Croatia's Ivan Dodig 6-7 (2), 6-1, 6-4 on the fifth day of the Brisbane International.
The fourth-seeded Canadian advanced to the quarter-finals and will next meet Lucas Pouille, who upset sixth-seeded David Goffin 7-6 (5), 4-6, 6-3.
Roger Federer finally opened his 2016 season with a commanding 6-2, 6-1 win over German qualifier Tobias Kamke, and advanced to a quarter-final against Grigor Dimitrov, who beat Viktor Troicki 5-7, 7-6 (6), 6-2 earlier Thursday.
The 17-time major winner converted five of his six breakpoint chances and saved the only one he faced against Kamke, finding his touch quickly and dispelling pre-match rumours that he might be carrying an injury.
While the top-ranked women have succumbed to injuries or inconsistency in the first week of the season, Victoria Azarenka has maintained her surge in form.
The two-time Australian Open champion reached the Brisbane International semifinals by beating eighth-seeded Roberta Vinci 6-1, 6-2.
She has dropped just 10 games en route to the semis, where she'll meet Samantha Crawford, a U.S. qualifier who beat Andrea Pektovic 6-3, 6-0.
Azarenka, who was limited to 23 tournaments across the last two seasons because of injuries, was broken once in each set but converted seven of her 11 breakpoint chances against Vinci, who ended Serena Williams's bid for a true Grand Slam in the U.S. Open semifinals.
"I really had to take control in my own hands, because she comes up with some really difficult situations and combinations which keep you on your toes," Azarenka said.
Fourth-seeded Angelique Kerber advanced past Anastasia Pavlyuchenkova 6-4, 6-4, and will next play No. 6-seeded Carla Suarez Navarro, who held off Varvara Lepchenko 4-6, 6-4, 7-5.
Wozniacki sharp in Auckland
At the ASB Classic in Auckland, New Zealand, third-seeded Caroline Wozniacki reached the semifinals with a 6-1, 6-0 win over Alexandra Dalgheru.
"I really hit it well, I went for my shots," said Wozniacki, who made only eight unforced errors. "I came to the net — I didn't even know I could volley like that, so I was pleasantly surprised."
Wozniacki has a 5-0 record against her semifinal opponent, Sloane Stephens, who advanced 7-6 (6), 6-3 over British qualifier Naomi Broady.
In other quarter-finals, Tamira Paszek beat fellow qualifier Kirsten Flipkens 6-4, 6-7 (3), 6-3 and Julia Goerges outlasted Nao Hibino 6-7 (3), 6-2, 6-4.