Daniela Hantuchova came from behind to beat Jelena Jankovic in the first round of the Pan Pacific Open on Tuesday.
Hantuchova is unhappy about the players' Tour schedule
The Slovakian, who went out to Maria Sharapova in the fourth round of the Australian Open, struggled in the first set losing it 6-2 to the Serbian.
But the sixth seed quickly adjusted to the speed of the surface, powering through the next two sets 6-4 6-4.
Title holder Sharapova has a bye in the first round. Martina Hingis is a wildcard entry for the tournament.
Hantuchova said she was pleased to make it through to the last 16 of the Tokyo event.
"I tried to hang in there and wait for my chances," she said.
"I kept fighting and tried to be more aggressive and go for my shots."
Hantuchova also lent her voice to growing criticism of the heavy schedule on the WTA Tour.
"Everyone knows the season is too long," the former world number five said. "It starts in January and ends in November. We're still people. We're not robots."
Hingis reached the quarter-finals in Australia, just weeks after her return to the game.
The former world number one, who retired due to injury in 2002, faces unseeded Korean Yoon Jeong Cho.