Naomi Osaka has been brought back to earth with a bump, crashing out in the second round of the Brisbane International in her first tournament since becoming a mother.

The two-time Australian Open winner looked assured when she took a one-set lead against Czechia’s Karolina Pliskova in Brisbane on Wednesday.

But her hard work soon unravelled, with Pliskova winning a tiebreak in the second set and holding on after an early break in the third to claim a 3-6 7-6 6-4 victory.

“I was happy to start with a win,” said Pliskova, who qualified for the third round, where she will face either Jelena Ostapenko or Camila Giorgi.

“I thought I played quite well. There’s a lot of things to improve on, but that was a good start.”

The match was just Osaka’s second in 15 months after giving birth to daughter Shai last July.

The Japanese won her opening-round match against Germany’s Tamara Korpatsch in straight sets.

But against her fellow former world No.1 she showed signs of sloppiness, with Osaka converting just two of 12 break points offered to her through an absorbing two-and-a-quarter-hour contest.

The silver lining for Osaka is the fact her service game looked to be back to its best, the 26-year-old raining down 14 aces.

Elsewhere, Australia’s Daria Saville showed some resistance against Anastasia Potapova, forcing the Russian to a third set before falling to a 6-4 6-3 6-4 loss.

Later in Brisbane, reigning Australian Open champion Aryna Sabalenka will get her tournament under way against Lucia Bronzetti of Italy.

Meanwhile, rising Queenslander Olivia Gadecki is also in action, aiming to take down Kazakhstan’s world No.3 Elena Rybakina.

-AAP