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Ashleigh Barty and Elise Mertens, the two champions of the Melbourne Summer Series one week ago, continued their strong form to move into the fourth round of the Australian Open with straight-sets defeats of fellow seeded opponents.

No.1 seed Barty, who captured her second title on home soil at the Yarra Valley Classic, came from a break down in both sets to navigate past the dangerous No.29 seed Ekaterina Alexandrova 6-2, 6-4. Gippsland Trophy winner Elise Mertens was even more efficient, racing past No.11 seed Belinda Bencic 6-2, 6-1 in just 62 minutes.

Both matches were characterized by intelligent, all-court tennis from the victors, who share an ability to out-maneuver opponents by thinking their way back into points from defensive positions. Barty, intermittently outgunned by the hard-hitting Alexandrova, used her trademark slice to fine effect to negate the Russian's power, at one point responding to a sharp angle by knifing a clean sliced winner down the line. In this manner, the Australian was able to overturn 0-2 and 2-4 deficits in the first and second set respectively.

"That was going to be a big point of difference for me tonight," Barty said of her slice. "It was something [coach Craig Tyzzer] and I spoke about, that we were going to go ahead and try to use that slice as often as possible, not only to change up the tempo of the match but also put the ball in different positions. It's obviously something I love to play around with. At times I overuse it, so it's about getting that balance right, but I felt like tonight it was spot on."

As a result, Barty has quietly hit a milestone of consistency. Since making her first Grand Slam second week at the 2018 US Open, the World No.1 has reached at least the fourth round of seven majors in a row that she has contested. Only three active players have longer such streaks: Serena Williams (18, between the 1999 US Open and 2005 Australian Open), Kim Clijsters (14, between the 2002 and 2009 US Opens) and Venus Williams (13, between the 1997 US Open and 2001 Australian Open). Only Venus's streak dated, like Barty's, from her second-week debut.

Elise Mertens waits to return Belinda Bencic's serve en route to a straight-sets win.

Photo by Tennis Australia/Scott Barbour

Mertens has also been a model of consistency of late - particularly since the Tour resumption last August. Since then, the Belgian has won 30 matches, including her current winning streak of seven - more than any other player. Against Bencic, the 2018 semifinalist played a cerebral and near-flawless match, tallying a ratio of 22 winners to just seven unforced errors and racking up seven aces. "I really had to stay in my bubble, do my thing," she said afterwards. "My first serve was working today, so I had an advantage with that. It was just a good day at the office."

Mertens seemed to be one step ahead of her opponent at every stage: at one point a defensive short slice proved to merely be the set-up for a pinpoint lob. A projected quarterfinal between Barty and Mertens is sure to be a fascinating battle of brains as well as bodies.

Shelby Rogers pounds a forehand against Anett Kontaveit.

Photo by Getty Images

First, Mertens needs to find a way past the finesse of No.25 seed Karolina Muchova, whom she defeated in Ostrava last autumn, while Barty faces a rematch of last week's Yarra Valley Classic quarterfinal against the unseeded Shelby Rogers. The American started slowly against No.21 seed Anett Kontaveit, falling behind 1-4, but once her game clicked proved more versatile in terms of both offence and defence as she roared back to win 6-4, 6-3.

Rogers, who reached her second Grand Slam quarterfinal at the US Open last year, conceded her first service game but would not face another break point in the match, and was particularly impressive in going after her shots to press home her advantage. Breaking Kontaveit for the win, the World No.57 pulled two stunning winners, on return and on a down-the-line backhand, to put herself in position to close the contest out.

This was Rogers' first win over Kontaveit in three attempts - and she'll need to overturn another 0-2 head-to-head in the next round against Barty, with both their previous meetings also occurring on Australian hard courts. Nonetheless, the 28-year-old could draw hope from their Yarra Valley encounter last week, in which she took Barty to a match tiebreak before falling 7-5, 2-6, [10-4].