The Belarussian surged up the WTA rankings past year, winning her first two titles and ending it just outside the top 10 and arrived in Melbourne fresh from winning in Shenzhen. Although Istomin is now ranked 99th in the world ratings, Federer will still be on guard after the 32-year-old player from Uzbekistan stunned six-time champion Djokovic in the 2nd round of the 2017 Australian Open.
It was an incident that overshadowed Naomi Osaka's maiden grand slam triumph and split opinion among fans and pundits alike.
That loss left Williams, who also lost in the Wimbledon final a year ago, short of matching Margaret Court's marker of 24 grand slam titles, a record the American has another chance of equalling in Melbourne over the next fortnight. Williams, seeded 16th this year, later gave birth to her daughter that year and skipped Melbourne while recovering from complications during birth. It was her 23rd Grand Slam championship.More news: Far-right German politician seriously injured in gang attack
"But there will be a side note that Serena has a lot of passion and that she has at times lost her cool on the courts, but I don't think for one minute it's going to tarnish her whole reputation".
Williams reached the finals at Wimbledon and in NY on what was her comeback year on the WTA Tour in 2018 following the birth of her first child. "I am looking ahead to more great things from Serena", said McEnroe.
"She has had time off, she can really get away from tennis, before maybe not as much". While she is the leading light for the next generation, the world number four´s status as second favourite points to a lack of serious rivals for Williams among the more established players.More news: Bayern Confirm They Want To Sign Chelsea Attacker
"I noticed she seems fitter, which is a scary thought". She warmed up for Melbourne by making the semi-finals of the Brisbane International last week, where she blamed a poor attitude for losing to Lesia Tsurenko.
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"I would say this is yet another chapter in the incredible story of Serena Williams, a lot of positives, a few negatives, no doubt that [US Open controversy] was a negative", he said.More news: Still time to get flu shots: Sherlock
As far as the final match is concerned, in-form Angelique Kerber of Germany could be Williams' opponent.