MELBOURNE ­– Five quick thoughts from a wacky Day 4 at the 2018 Australian Open.

• In 2019, tennis’ majors will pare back to 16 seeded players from the current 32. The rationale: this will breed more first round upsets and more competitive matches. True as that may be, this event suggests that no more randomness is needed. This tournament has been a big bowl of close matches. Grigor Dimitrov, the third seed, needed to go 8-6 in the fifth set to survive Mackie McDonald, a former NCAA champ from UCLA who needed to qualify. Caroline Wozniacki staved off two match points to survive her second round match. And then there have been the actual upsets, wrecking balls that have been leaving gaping holes in the draw. Today’s headline—so far; we need to time stamp this—is Su-Wei Hsieh taking out No. 3-seed Garbine Muguruza, 7-6(1), 6-4. Muguruza is a woman of mystery and a woman of extremes. She tends either to win majors or lose early. On Thursday, she seemed flustered by the heat, her blisters, and a tricky opponent, and fell in straight sets.

• Speaking of mystery, this marks Novak Djokovic’s first tournament in a half-year and, as for the verdict…. the jury remains sequestered. He has looked dazzling for stretches, like the player who is a six-time champ here. He has looked dismal for stretches as well; to wit the first set of his match against Gael Monfils on Thursday. There are times when Djokovic appears unbothered by his right elbow, his service speed comparable to pre-injury rates. There have been other times when you fear he is still impacted. Regardless, won today, beating Monfils, 4-6, 6-3, 6-1, 6-3. And he remains in the draw, which is all that matters. Albert Ramos-Vinolas of Spain is up next.

• With Serena Williams (and Victoria Azarenka) out, Maria Sharapova and Angelique Kerber are the only two players in the women’s draw to have won this event previously. Through two rounds, both look like good bet to win it again. Sharapova exacted revenge on Anastasija Sevastova, her vanquisher at the U.S. Open, winning 6-1, 7-6(4). She played a terrific set of tennis and then a “battle set.” Better still, she did so in 80 minutes, conserving energy. Kerber, meanwhile, has continued to wipe her hand clean of 2017. She won her seventh match of the season, taking down Donna Vekic on Thursday. The hitch: Kerber and Sharapova play each other on Saturday.

• A disappointing tournament for the Americans continued as Sam Querrey lost, unaccountably, to Marton Fucsovics, a Hungarian ranked No. 80. There have, though, been some encouraging results. Denis Kudla took two sets off of a top five player, Dominic Thiem, before capitulating in five sets. Lauren Davis won the last 12 games to defeat Andrea Petkovic 4-6, 6-0, 6-0. And how about Bernarda Pera knocking off No. 9-seed Jo Konta 6-4, 7-5. Born in Croatia, Pera, 23, lost in qualifying and was booking a ticket to go home when she got a call informing her of a lucky loser spot. Suffice to say she’s made the most of it. Next up: Barbora Strycova.

• Lost amid the match results, the WTA made a significant announcement on Thursday. After 2018, the year-end championship will relocate from Singapore to Shenzhen, China, for the next ten years. While this is an extraordinarily long commitment, it is also extraordinary amount of money. (Thanks, public financing!) The $14 million purse represents a doubling from the current prize money; and it’s significantly more than the men make for the ATP World Tour Finals in London. Asked about the length of the deal, WTA CEO Steve Simon said: “Yeah, 10 years is a long time. I think I have said this before. For events to be truly successful and for people to invest behind the event, you need time. And if you look at our most successful events in this sport, they traditionally have a long history. You could even look at our friends on the ATP and the success they had in London, where it's now been for 10 years, and look at how that event has grown. We went into the marketplace with the idea that this would be a long-term agreement, and we found the marketplace was much more excited about that.”