MELBOURNE, Australia - For the 19th time in 20 appearances at the Australian Open, No.8 seed Serena Williams booked her place in the third round, this time with a 6-2, 6-3 defeat of Tamara Zidansek in one hour and 18 minutes to extend her winning streak to seven matches.

The 23-time Grand Slam champion's only loss before the round of 32 here came on her Melbourne debut in 1998, when she upset No.6 seed Irina Spirlea in the first round but fell to sister Venus in the second; nor has she lost before the third round in any major since falling to Garbiñe Muguruza in the second round of Roland Garros 2014. Today, in her first meeting with Zidansek, Williams showed off both her shotmaking and her battling qualities, striking 25 winners and seven aces while coming through a competitive second set.

"I just started making way too many errors," said Williams of her second-set struggles. "I mean, more errors than I have been making in my good matches in the past. I just wasn't doing the right technique, catching the ball not in my strike zone. It was just all off so I had to adjust... So just having to say, OK, not every match is going to be perfect, how to work through that. I hadn't done that since September. It was just kind of working through that and getting through that."

It began in dream fashion. An array of dazzling winners garnered the American eight of the first 10 points and an immediate break, with her delicate touch on a pair of drop-volleys particularly impressive.

Even when Zidansek upped her game, absorbing Williams's pace and sending it back for a few sweet forehand winners, the former World No.1 remained in control of the scoreboard, with a service winner saving a break-back point in the fourth game and errant forehands from the Slovenian sealing a double break for 4-1. The Auckland champion would miss a set point at 5-1, but served out the opening set to 15 with little drama.

However, the 22-year-old World No.70's game - a blend of scrappy defence, sudden injections of pace and a judicious sprinkling of dropshots - would remain a thorn in Williams's side. With Zidansek mixing up pace and spin, Williams's groundstrokes were thrown off-kilter, and the second set found her battling her own errors as well as an opponent who had settled into her rhythm.

A war cry as the seven-time champion nailed a backhand down the line was an indication of how much she was now needing to scrap as Zidansek fought off the first seven break points against her of the second set, taking a 3-2 lead.

This set the stage for the most gripping - and crucial game of the contest, a four-deuce tussle on the Williams serve that was paused midway through for the Rod Laver Arena roof to be closed fully. Anticipating brilliantly, Zidansek came out on top of a number of thrilling rallies and held three break points for 4-2.

But despite a number of poor mistakes, particularly on the drive volley, Williams stepped up in crunch time as she has so many times before. Service winners staved off the first two and a brilliant backhand winner the third, before the 38-year-old put away a forehand to get out of the game.

That would be Zidansek's last stand: the Nurnberg runner-up faded as Williams pressed home her advantage to rattle through 12 of the last 15 points of the match. As if to exorcise the memories of the missed break points earlier in the set, Williams threw herself into her returns with even greater gusto, nailing a clean forehand winner off one on her first match point to set up a third-round date with No.27 seed Wang Qiang.

"It's definitely pretty deep," Williams said of the internal dialogue she used to get through the second set. "It has to be motivating but also realistic. Sometimes you just miss some shots, you don't know why. Just trying to find an answer. That's what I kept doing. Thankfully I was able to find an answer in the middle, right in the middle of the second set."

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