Defending champion Angelique Kerber endured a nervy return to Rod Laver Arena on Monday, while there was more Melbourne misery for Simona Halep in the first round of the Australian Open.
Kerber's victory 12 months ago proved a catalyst for a superb 2016 that also yielded success at the US Open, final appearances at Wimbledon and the Rio Olympics and a rise to number one in the world.
The German was coasting in her opening tie against Lesia Tsurenko, but eventually had to come through an uncomfortable three-set encounter.
As Kerber survived, there was no such luck for fourth seed Halep, who became the biggest casualty of the opening round against Shelby Rogers.
STUTTERING KERBER TOUGHS OUT TSURENKO TEST
Kerber's success in 2016 saw her overhaul Serena Williams at the top of the world rankings, but the powerful left hander had to dig deep for a 6-2 5-7 6-2 win.
Tsurenko appeared down and out when Kerber won seven straight games for a 6-2 2-0 lead, but she faltered when serving for the match at 5-4.
However, Kerber regained her composure in the final set to ensure there was not a major upset.
"To be honest, when I had the match point and then went into a third, I was thinking about my match one year ago [when she saved a match point against Misaki Doi]. First rounds are always tough, but I'm happy I won the match," she said.
ROGERS ROCKS HAPLESS HALEP
It was a case of deja vu for Halep as she was put to the sword by Rogers in a 6-3 6-1 defeat.
Halep was defeated by qualifier Zhang Shuai in the first round in Melbourne 12 months ago and the Romanian, battling a knee injury, was evidently short of match practice against a calm and collected Rogers.
Following her surprise win, the world number 52 said: "I think I played great. My game plan worked. Just move forward, hit your shots, be really aggressive. When I'm doing that, I am playing well."
Halep was not the only seed to fall at the first hurdle. Roberta Vinci (15) - a 2015 US Open finalist - lost to Coco Vandeweghe, while Kiki Bertens (19), Daria Kasatkina (23) and Laura Siegemund (26) also lost, the latter to former world number one Jelena Jankovic.
MUGURUZA SURVIVES, VENUS BATTLES THROUGH
The seventh seed was not always able to display her trademark powerful groundstrokes, while her timing also appeared hampered as she battled back from 4-1 down in the second set.
"It was very tough. You're playing, then suddenly you start to feel pain in your body. Obviously I was nervous, so I just tried to be calm, to have a good attitude and keep fighting," Muguruza said.
Venus Williams was playing just her second match of 2017 due to a right-arm injury and fought to a 7-6 (7-5) 7-5 win over Kateryna Kozlova, who had the chance to serve for the first set.
Williams was later told that Kozlova, 22, was born when she turned professional in 1994 and said: "You're trying to make me feel old! I really have to give her a lot of credit for playing a match that was not a lot of errors and just relentless."
While Muguruza and Williams toiled, there were no such problems for Svetlana Kuznetsova (8) and Carla Suarez Navarro (10), the former defeating Mariana Duque-Marino 6-0 6-1 and the latter accounting for Jana Cepelova 6-2 6-2. Elina Svitolina (11) was equally comfortable in a 6-0 6-2 win over Galina Voskoboeva.
LOCAL FAVOURITE ENJOYS DREAM SLAM DEBUT
The Melbourne crowd was able to celebrate a local hero as 17-year-old Jaimee Fourlis defeated Anna Tatishvili 6-4 6-3 in her first grand-slam match.
Queenslander Ash Barty also reached round two by beating Annika Beck, but fellow Australian Destanee Aiava - the youngest player in the draw at 16 - fell short against Mona Barthel.