Victoria Azarenka and Serena Williams both suffered scares before securing their places in the second round of the Australian Open.
Tournament favourite Williams was not troubled in the slightest by opponent Edina Gallovits-Hall, winning 6-0 6-0, but by a right ankle injury which required lengthy treatment after a heavy fall on Hisense Arena.
Azarenka, the top seed, was given a tougher-than-expected ride by Monica Niculescu before coming through 6-1 6-4 after a second-set wobble.
"I started really well but the second set was a struggle" - Victoria Azarenka
Having romped into a 4-0 lead, it appeared plain sailing for Williams, a five-time champion in Melbourne, before she slipped on her already strapped ankle chasing down a forehand and crashed to the ground.
She eventually limped back to her seat and the trainer removed the bandaging from her foot to administer treatment.
After having the strapping re-applied, Williams was okay to continue and she showed little discomfort as she hammered three colossal forehand winners in the next four points on her way to a third break and a 5-0 lead.
Williams received more treatment at the change of ends but held to 15 to seal the first set.
The second set started just as the first had - with Gallovits-Hall double-faulting to give Williams an opening break.
She broke to love in game three and had help from yet another Gallovits-Hall double - her eighth - to make it 5-0, before serving out another love game to complete the most comprehensive of victories in 54 minutes.
Next up for Williams - assuming there is no lasting damage to her ankle - will be either Slovakia's Magdalena Rybarikova or Garbine Muguruza of Spain.
Defending champion Azarenka seemed set for an equally convincing scoreline when she ran through the first set with minimal fuss.
But Romanian Niculescu surprised everyone inside Rod Laver Arena by swiftly establishing a 3-0 second-set advantage. It almost became 4-0 but Azarenka clung grimly on to her serve by staving off two break points.
It proved a turning point as the world number one, roared on by close friend Redfoo from the band LMFAO, hit back.
She drew level at 3-3, prompting a frustrated Niculescu to crack her racket into the court - an act which earned her a warning from the chair umpire.
Azarenka then broke again for 5-4 as Niculescu's challenge waned and she served it out to advance.
It was her first appearance on RLA since her thrashing of Maria Sharapova in last year's final and Azarenka admitted she was pleased to have avoided an embarrassing return.
"It's great to be back, there were a lot of overwhelming emotions out there," she said.
"I started really well but the second set was a struggle. I am pleased to get through."
Former world number Caroline Wozniacki also progressed but only after a wonderful deciding-set comeback against Sabine Lisicki.
Lisicki led 3-0 in the third only to run out of steam as 10th seed Wozniacki hit back to clinch a morale-boosting 2-6 6-3 6-3 triumph.
Eighth seed Petra Kvitova overcame Francesca Schiavone in three sets in a battle of former grand slam champions, 14th seed Maria Kirilenko ousted Vania King and 16th seed Roberta Vinci overcame Silvia Soler-Espinosa.
There were a couple of shocks, though, with seventh seed Sara Errani, a quarter-finalist here last year, and 12th seed Nadia Petrova both going out in the first round.
Errani was beaten 6-4 6-4 by Spain's Carla Suarez Navarro while Petrova was thrashed 6-2 6-0 by Japanese veteran Kimiko-Date Krumm.
At 42, Date-Krumm became the oldest winner of a women's singles match in the tournament's history.
"I'm very happy to win today, but I don't play for the records," she said. "Even when I lose, I still enjoy it. Of course, every time I lose...it's tough. But still I enjoy playing.
"I love tennis. I like practice. I like games. I like the tour. I enjoy it a lot."