Six-time Australian Open champion Serena Williams avoided the upset bug as a top two seed in the men's and women's singles draw, with the shock exits of Andy Murray and Novak Djokovic in the men's singles, and defending Australian Open champion Angelique Kerber fell by the wayside to compatriot Coco Vandeweghe.

The second seed is the firm favorite to regain the Australian Open title, and she has to win the title in Melbourne to regain the world number one ranking. Nevertheless, Williams overcame a tough test with 16th seed Barbora Strycova to reach the quarterfinals in Melbourne for the 11th time in her career.

Williams snatches a tough opening set

The 22-time Grand Slam champion opened proceedings in the first match of the day in the Rod Laver Arena, and she lost serve immediately to 15, and Strycova would follow suit, with Williams leveling the game at 1-1. Furthermore, in the third game of the match, the second seed would get broken to love, and for the fourth consecutive game of the match, there was a break of serve with the American breaking Strycova back once more.

The former world number one would finally stop the rot by holding serve to lead 3-2. Strycova would also hold for the first time in the next game, leveling the match at 3-3. However, for the third time in the match, the 30-year-old would break Williams' serve with three unforced errors causing the former world number one problems.

In the following game, the second seed would get a 0-15 lead on the Czech's serve with a good return of serve and forehand winner in the corner. Furthermore, there continued to be errors from both players. Williams was looking to get the immediate break back with coming out on top in a 14-shot rally, finishing the point off with a drive volley. A good first serve out wide from Strycova saved it but aggressive forehands from the American-created another break point. The American would take it, getting the game levelled at 4-4.

In the business end of the set, the 35-year-old's forehand continued to break down creating another forehand unforced error out wide. However, the six-time champion would win the next two points with forehand winners. An ace out wide, followed by strong hitting caused errors from Strycova to lead 5-4.

The 16th seed had never won more than four games in a set against Williams, and the signs looked ominous as the American began the game with a forehand return winner down the line on Strycova's second serve. More unforced errors from both players handed the American her first set point at 30-40. A backhand unforced error in the net allowed the Czech to save it. Once again, Williams applied more pressure on Strycova, getting another set point chance but it was snuffed out with a good serve out wide.

Strycova was competing in her third Grand Slam fourth round match (Photo by William West / Getty Images)
Strycova was competing in her third Grand Slam fourth round match (Photo by William West / Getty Images)

Williams would get a third break point chance but it was quickly snuffed out again with an ace out wide, however, the net cord helping Williams' forehand winner go down the line to get a fourth set point. A serve out wide and volley winner at the net, allowed the Czech number three to save it. She eventually held to serve in a game lasting 10 minutes with a forehand winner down on the line in an 11-shot rally, gaining an applause from the 22-time Slam champion.

The six-time champion erased that game from her memory as she served held her serve easily, and getting an ace out wide to lead 7-6-5, and put the pressure immediately back on Strycova.

Williams was determined to not go to an opening set tiebreak and she raced out to a 0-40 lead on Strycova's serve, creating three more set point opportunities. However, the Czech didn't have to do much to save the fifth and sixth set points as Williams committed a backhand and unforced error in the net. Strycova employed the serve and volley tactic, drawing the error from the former world number one saving an impressive seven set points. Inevitably, Williams would get an eighth set point with a backhand return winner down the line, and the net cord, truly working in the American's favor to win a hard-fought opening set, 7-5 in 55 minutes.

The second seed reaches the 11th quarterfinal in Melbourne

In contrast to the horror show of serving in the opening set, Williams and Strycova both held their opening services games with ease. The American would begin the third game of the set with a forehand unforced error narrowly missing the line. However, a backhand unforced error, an ace out down the T and a forehand unforced error gave Williams a couple of game points. The second seed would extend her lead to 2-1 with a backhand winner down the line.

The pressure was mounting on Strycova in the fourth game but Williams committed more unforced errors to allow the Czech to have a 40-15 lead. However, the American would get the game level to deuce, drawing the errors from Strycova. Another forehand unforced error from Williams gave the 16th seed another chance to hold serve. Moreover, the second seed would get a forehand return winner down the line and she would come out on top in an impressive 14-shot rally with a stretch winner down the line to create a break point. Williams wouldn't hesitate and immediately took the break with a volley error at the net from Strycova to lead 3-1.

Williams committed over 40 unforced errors (Photo by William West / Getty Images)
Williams committed over 40 unforced errors (Photo by William West / Getty Images)

The 35-year-old continued to hit the ball extremely hard, drawing the errors from Strycova, and she would consolidate the break easily, leading 4-1 in a commanding position. However, the sixth game of the second set sprung unforced errors from both players, and the Olympic bronze doubles medalist ensured that the break was only one and she was trailing 4-2.

In the seventh game of the second set, the second seed didn't have too much to do as both players would commit more errors but Williams would get a forehand passing shot winner down the line at 40-15, followed by a double fault and a poor unforced error at the net from Strycova, handed Williams at 5-2 lead.

Strycova was serving to stay in the match but she was simply given the game as Williams' forehand continued to break down as she committed four consecutive unforced errors, allowing Strycova to hold to love.

The six-time champion was serving for the match, and she got off to a good start with a 15-0 lead by virtue of a backhand unforced error from the 16th seed. Surprisingly, Williams would lose the next three consecutive points with a poor drop shot allowing Strycova to get a volley winner at the net. Two unforced errors handed Strycova, two break-back points to keep the match alive. Williams would get a smash winner at the net to save the second set, however, a forehand unforced error out wide got Strycova back on serve at 5-4.

Williams and Strycova shake hands at the net (Photo by Clive Brunskill / Getty Images)
Williams and Strycova shake hands at the net (Photo by Clive Brunskill / Getty Images)

Williams started the tenth game on Strycova's serve with intent with a backhand winner down the line, wrongfooting the feisty Czech. However, a backhand unforced error in the net, followed by a great pick-up backhand winner down the line gave Strycova a 30-15 lead and the shot was applauded by Williams. A forehand smash at the net from the American forced the error from Strycova, followed by an unforced error in a 13-shot rally handed Williams her first match point. The 22-time Grand Slam champion took it at the first time of asking with a backhand down the line, forcing the error from Strycova to win 7-5, 6-4 in an hour and 45 minutes, reaching her 11th Australian Open quarterfinal in the process.

Match Stats

It wasn't the strongest of serving days for the second seed and favorite for the title as she got 45 percent of her first serves in and winning 65 percent of the points on it. She produced 28 winners and committed 46 unforced errors which aren't expected from the former world number one. Strycova only hit nine winners and 14 unforced errors.

The quarterfinals await

It wasn't the best performance from Williams as her performances against Belinda Bencic, Lucie Safarova and Nicole Gibbs in the first three rounds were clinical, the American dug deep and found a way to win against Strycova, who played a very good match. The six-time champion will be competing in her 47th Grand Slam quarterfinal against ninth seed Johanna Konta for the first time in her career. Williams will need to get back on the practice court and work on those forehands if she's going to lift the Daphne Akhurst Memorial Trophy on Saturday for an unprecedented seventh time.