BRISBANE (AFP) -- Rafael Nadal said every day was an adventure as his comeback from injury gathered pace with an aggressive 6-1, 6-2 drubbing of Australian Jason Kubler at the Brisbane International on Thursday, Jan. 4.

Played in hot and humid conditions on Pat Rafter Arena, the Spanish great took 1hr 23min to see off Kubler, who battled hard but didn't have the weapons to trouble the 22-time Grand Slam champion.

Nadal, 37, has not played on tour since suffering an injury at the 2023 Australian Open a year ago, resulting in two surgeries on his hip.

"Every day is an adventure," he said of his comeback. "I take every day like an opportunity, and tomorrow is another one."

Nadal said leading into the tournament that he had no expectations for the Australian summer.

But the form he showed against former US Open champion Dominic Thiem in the first round and now Kubler suggests he could be a real threat at the first Grand Slam of the year at Melbourne Park.

He raced to a 5-0 lead in the first set before Kubler got on the board, then broke the Australian's opening game of the second to stamp his authority on the match.

"I started the match playing very well, with very good determination," Nadal said. "I tried to be aggressive from the baseline and I think it worked very well.

"I think it was a very positive match for me. Two victories after a long time being outside the professional tour is something that makes me feel good."

He said his body was holding up well after the two matches.

"The positive thing is that the first two matches haven't been super long," Nadal said.

"Of course, I had some feelings after the first match. I mean, I have been a year without playing with the tension of a real match, so I felt a little bit some muscles tired here and there.

"In general terms, I felt good."

The only real blemish for the Spaniard was a warning for a time violation for taking too long to return to court after a bathroom break at the end of the first set.

He later explained the humidity was so high that he had to do a complete change of clothes and was four seconds longer than he should have been.

Nadal will next play Australian Jordan Thompson in the quarterfinals and remains on course for a blockbuster semifinal against second-seeded Bulgarian Grigor Dimitrov, who demolished Germany's Daniel Altmaier 6-1, 6-2.

Ostapenko beats heat

Dimitrov next meets Australian wildcard Rinky Hijikata, who bounced back from losing the first set to see off Czech qualifier Tomas Machac 5-7, 6-2, 7-6 (7/4).

In the women's draw, Latvia's Jelena Ostapenko ended Karolina Pliskova's title defence when she downed the Czech star 6-4, 4-6, 6-3 to book a quarterfinal against Victoria Azarenka.

The 26-year-old former French Open champion needed assistance from the trainer during the third set as she struggled with the heat and humidity.

But she managed to recover enough to overcome Pliskova in 2hr 13min.

"I'm coming from winter where it's minus 15 right now and here it's 35 degrees," she said.

Former world number one Azarenka survived a stern challenge from unheralded Frenchwoman Clara Burel before winning 7-5, 6-2.

Top seed Aryna Sabalenka looked in superb touch as she thrashed China's Zhu Lin 6-1, 6-0, as did second seed Elena Rybakina, who beat Elise Mertens with the same scoreline.

There were also wins for the Czech Republic's Linda Noskova, Russia's Anastasia Potapova and 16-year-old rising star Mirra Andreeva.