MELBOURNE, Australia -- Coming in, with all the offseason chaos, this Australian Open looked like one of the most unsettled and unpredictable in recent memory. And then, when they actually started playing Monday, things really got funky.
In the tournament's first marquee match, at Rod Laver Arena, No. 4 seed Simona Halep was stunned by American Shelby Rogers 6-3, 6-1, only 75 minutes into the fortnight.
Rogers, of Charleston, South Carolina, is ranked No. 52 among WTA players. She simply overpowered Halep, stroking 26 winners and breaking her serve four of eight times. Strictly in terms of ranking, it was the biggest win of Rogers' career.
"It's no surprise to me," Rogers, 24, said in her postmatch interview. "I have had some tough draws in the slams, so I'm kind of used to that, playing the seeds and playing big matches right off the bat. Yeah, I think I played great today.
"My game plan worked. Just move forward, hit your shots, be really aggressive. When I'm doing that, I am playing well. Very happy with how I did today."
A year ago this time, Rogers was playing minor ITF events.
Last year, Rogers advanced past the second round only twice -- but it happened at two of the year's biggest events, the French Open and the Olympics in Rio de Janeiro. Rogers was a revelation in Paris, beating formidable seeds such as Karolina Pliskova and Petra Kvitova to reach the quarterfinals.
Advancing deep at Roland Garros, she said, gave her some valuable confidence.
"The biggest thing I took away from that was just that I can compete with the top players in the world and I'm good enough," Rogers said. "And little things here and there I need to work on, but I'm here. I need to believe in myself.
"Just trying to keep that going."
Halep beat Rogers in straight sets in the third round of last year's US Open, their only previous meeting.
And now Rogers has produced another major effort, defeating Halep, who is now a disappointing 17-10 in the first round of Grand Slams. A year ago, Halep fell in the first round here to Chinese qualifier Zhang Shuai, who had been 0-14 in major matches and was ranked No. 133 at the time.
Entering the tournament, there was a scenario by which Halep could have vaulted over Serena Williams and Angelique Kerber to the No. 1 ranking.
Rogers will next play the winner between Australian wild-card entry Ash Barty or Annika Beck of Germany in the second round.
No. 1 seed Angelique Kerber struggled to advance. Ultimately, she rallied to defeat Lesia Tsurenko 6-2, 5-7, 6-2 in the first night match at Rod Laver Arena.
The defending Australian Open champion had lost two of her three previous matches in 2017.
A year ago, Kerber also started slowly and was forced to save a match point in her first-round match against Misaki Doi.
"To be honest, I was thinking about this," Kerber said. "When I lost the second set, and I had match point, I was thinking about my match last year in the first round -- first rounds are always tough."
Kerber, who turns 29 in two days, can guarantee her position at No. 1, ahead of Serena Williams, by reaching the finals here.
In the second match at Rod Laver Arena, No. 13 seed Venus Williams trailed early but came back to defeat Kateryna Kozlova 7-6 (5), 7-5. Williams, who turns 37 in June, sprayed a liberal 48 unforced errors in the match that ran one minute short of two hours.
"It's never easy playing the first round -- you're just trying to find the rhythm," Williams said. "She played amazing. It's very satisfying to get through a match against an opponent who is on fire."
Williams lost in the first round of the Australian Open last year to eventual semifinalist Johanna Konta. She's making her 73rd appearance in the main draw of a Grand Slam -- a record in the Open era.
American CoCo Vandeweghe overcame the heat and illness to beat 15th-seeded Roberta Vinci 6-1, 7-6 (3). Vandeweghe was down a break in the second set when she slumped to her knees, facing the backboard at Margaret Court Arena, and needed help from medical staff.
The trainer rubbed some water on Vandeweghe's neck as she stayed in the shade for a couple of minutes, not moving, before the tournament doctor went out to help.
After the match, Vandeweghe fell on her back and appeared to be crying. The doctor came out again to attend to her.
"Shoot. I don't know what was happening," Vandeweghe said in her on-court interview. "It wasn't the heat or anything. I just started feeling nauseous. I can't thank you guys [the crowd] enough for pushing me through that."
Seventh-seeded Garbine Muguruza saved a set point in the first set and needed a medical timeout before advancing with a 7-5, 6-4 win over Marina Erakovic, and 2014 Wimbledon finalist Eugenie Bouchard continued her recent resurgence by winning the last of the night matches 6-0, 6-4 against Louisa Chirico in 56 minutes.
Olympic gold medalist Monica Puig raced through her opening match, beating Patricia Tig 6-0, 6-1. Duan Yingying was among the early winners with a 6-3, 6-4 win over Rebecca Sramkova.
Australian teenager Destanee Aiava's milestone match ended in a 6-3, 7-6 (4) loss to German qualifier Mona Barthel. The 16-year-old Melbourne high school student became the first player born in this millennium to play a main-draw match at a major.
In two all-U.S. matches, Samantha Crawford defeated Lauren Davis 4-6, 6-3, 6-0 and Alison Riske beat Madison Brengle 7-5, 6-3.
Two other seeded players lost early women's matches, with Varvara Lepchenko beating No. 19 Kiki Bertens 7-5, 7-6 (5) and former No. 1-ranked Jelena Jankovic beating No. 26 Laura Siegemund 6-1, 1-6, 6-4.
Information from The Associated Press was used in this report.