Maria Sharapova recovered from a sluggish start to beat Venezuela's Maria Vento-Kabchi 7-6, 6-0 at the Pan Pacific Open at Tokyo on Wednesday.
Svetlana Kuznetsova trounced Swiss qualifier Marie-Gayanay Mikaelian 6-3, 6-1 to join her fellow Russian in the last eight of the $1.3 million tournament.
Sharapova struggled initially in her first match since losing to Serena Williams in last week's Australian Open semi-finals.
The Wimbledon champion dropped serve twice and was clearly frustrated with herself before finally taking control and racing through the tiebreak 7-3.
A more focused Sharapova powered through the second set in just 20 minutes, the 17-year-old closing out the match with her ninth ace.
Sharapova squandered match point in a crushing 2-6, 7-5, 8-6 loss to Williams in Melbourne. Williams went on to beat Lindsay Davenport in the Australian Open final at the weekend.
"It took a while to find my groove and rhythm," said Sharapova. "I just needed time after coming from the Australian Open but I picked up my level in the second set."
Kuznetsova was wrongly accused of doping violations last month and forced to play down talk of a rift with Sharapova during the Australian Open.
But the third seed looked comfortable from the start on Tokyo's indoor carpet as she pummelled Mikaelian into submission in just 49 minutes.
"It was tough playing my first match after the Australian Open," said US champion Kuznetsova, who was beaten by Sharapova in the Melbourne quarter-finals.
"I'm not playing too well yet but I'm not complaining -- I think I have the chance to win another Grand Slam this year."
The top four seeds received a first-round bye. World number one Davenport and Russia's Elena Dementieva play on Thursday.
In first-round matches, American Jill Craybas beat Russian Tatiana Panova 6-4, 4-6, 7-5. Japan's Akiko Morigami overcame Spaniard Maria Sanchez Lorenzo 6-4, 6-1.
