Tokyo - Former world number one Victoria Azarenka thrashed Australian Ashleigh Barty 6-4, 6-2 to reach the Pan Pacific Open quarter-finals on Thursday as she seeks a return to the top after giving birth in late 2016.
The Belarusian, who slipped further down the rankings as a result of a lengthy custody battle over baby Leo, will face either top seed Caroline Wozniacki, who is chasing a hat-trick of Tokyo titles, or Italy's Camila Giorgi in the last eight.
Wildcard Azarenka, currently 63rd on the women's WTA rankings, broke for 4-3 with a dipping backhand and clinched the opening set with a fizzing pass that landed on Barty's shoelaces, forcing the seventh seed to dump a forehand into the net.
Azarenka raced to a 4-1 lead in the second set and the two-time Australian Open champion delivered the coup de grace by jamming up Barty with a vicious kick serve into the ribcage on her second match point.
"That makes me feel a little old, but I'm happy to be here," said Azarenka, 29, when informed she had reached the quarter-finals for the first time since 2012.
"Obviously it's been a while since I've played, I'm just trying to look day by day and see what happens. But I'm definitely enjoying my time on court these days."
Earlier, Czech Barbora Strycova won a tempestuous encounter with Estonia's Anett Kontaveit 7-6, 3-6, 7-5 to set up a quarter-final against Japan's newly crowned US Open champion Naomi Osaka.
The Olympic doubles bronze medallist took the first-set tiebreak 7-5 but both players screamed in frustration at their wastefulness in a contest that lasted well over three hours.
Having used all her challenges, Strycova huffily staged a sit-down protest after Kontaveit saved one of eight match points with a passing shot that replays showed missed the line by some margin.
But the Czech returned to her task and closed out the match when Kontaveit whiffed a drive-volley far beyond the baseline.
"I know I will have to play very well to beat Naomi," said Strycova.
"She's a star - she's just won a Grand Slam, which was such a huge success for her. Playing in Japan the support will be for her but I'll try my best and see what happens."