Britain's Cameron Norrie says he could "barely practise" before his Australian Open defeat by Matteo Berrettini because of sickness.

Norrie, 29, lost 6-7 (4-7) 6-4 6-1 6-3 to the big-serving Italian in the first round on Tuesday.

The British number two said he became ill in Auckland, where he played a warm-up tournament before heading to Melbourne.

"It was not the best preparation," said Norrie, who reached the fourth round last year.

"I just hit the wall after an hour and a bit. I was not able to stay sharp on the court.

"It is a bit disappointing but it is what it is. Most importantly I need to get my health back to 100%."

Despite Norrie's defeat, there are still six Britons left in the Melbourne singles draws.

British women's number one Katie Boulter plays her first-round match later on Tuesday against Canada's Rebecca Marino.

Emma Raducanu moved into the second round despite struggling with her second serve, while Jack Draper, Jacob Fearnley, Jodie Burrage and Harriet Dart won on Monday.

Norrie's ambitions of stringing together some wins at the opening Grand Slam of the season were also hit by the tough draw.

Berrettini, the 2021 Wimbledon finalist and a former world number four, has suffered with injuries in recent seasons, but is back to 34th in the rankings and possesses one of the most potent serves on the ATP Tour.

Norrie created five break points in the match but was unable to take the Italian's serve.

"He's got a complete game. I think he can go really deep in the draw," said Norrie.

"I'm really happy that he's playing this level. He was very solid today.

"I was not able to sustain the physicality for four-and-a half hours, which is what it would have taken to beat Matteo."

Norrie reached a career-high of eighth in the world following a stellar 2022 season where he reached the Wimbledon semi-finals.

Hampered by form and fitness issues last year, he has now slipped to 52nd in the world.

But Norrie remains confident in his ability and is not worried about his falling outside of the top 60 after the Australian Open.

"I feel I'm hitting the ball as well as I can and I'm really happy with the work I've been putting in," said Norrie, who is unsure if he will be able to play in the Melbourne doubles alongside Marcus Willis.

"I feel clear in how I want to play and construct points. That's more important than the ranking."