British number one Johanna Konta made her earliest exit from the Australian Open by losing to Tunisia's Ons Jabeur in the first round.
Konta, seeded 12th, was beaten 6-4 6-2 by the tricky world number 78 at Melbourne Park.
The 28-year-old was playing only her second match in almost five months because of a knee injury.
Compatriot Kyle Edmund was also knocked out with a 7-6 (9-7) 6-3 7-6 (7-4) loss to Serbia's 24th seed Dusan Lajovic.
Konta struggled to settle as Jabeur knocked out Britain's highest-ranked player.
"It's important to recognise the season is long," Konta told BBC Sport.
"I'm not going to rush or sprint towards suddenly packing it all in. Things will come with time and putting the right work in."
Four other Britons play later on Tuesday, which features a packed schedule with 96 first-round matches needing to be completed after the opening day was washed out by heavy rain.
Katie Boulter, Heather Watson, Harriet Dart and Cameron Norrie should also play as planned with a much-improved weather forecast.
Rusty Konta unpicked by Jabeur
Konta, a 2016 semi-finalist at Melbourne Park, went into this year's opening Grand Slam having played only one match since September's US Open.
A tendonitis-like inflammation of the knee, which she suffered in the latter stages of last season, has had to be carefully managed.
Although she did not look troubled by the problem against Jabeur, Konta did show signs of rust and was unable to take her game to the levels that took her to the French Open semi-finals, along with the Wimbledon and US Open quarter-finals, last year.
Konta, who said afterward she was "pleased" with how her knee felt, hit 19 unforced errors, while Jabeur also punished her with 19 winners.
The Briton's serve came under immediate pressure from Jabeur, who is able to unsettle opponents with her variety, and she had to save a breakpoint in the opening game.
After steadying herself, an erratic game where she struggled on her first serve enabled Jabeur to strike and take the opening set.
Konta, backed by a healthy number of British fans, came out for the second set with renewed purpose, playing more aggressively to break in the opening game.
However, she was unable to back that up with a hold and from that point, Jabeur took control to win in just one hour and two minutes.
Enforced interruption costs Edmund
Like Konta, Edmund is also a former semi-finalist at Melbourne Park and his run to the last four in 2018 continues to be an anomaly here.
This was Edmund's fourth first-round exit in six appearances, with the other being a second-round defeat in 2017.
The 25-year-old Yorkshireman was leading 5-2 in the opening set on Monday before the match was postponed following the deluge of rain which decimated the day's play.
Edmund paid the price for the enforced interruption.
Passive play from the world number 65 allowed Lajovic to instantly fight back to 5-5 when they resumed in bright sunshine at Tuesday lunchtime.
The Serbian player, backed by raucous support which attempted to unsettle Edmund, edged a tight opener in a tie-break where a net cord worked heavily in his favour when the Briton was a mini-break up.
From that point, Edmund struggled to cope with Lajovic's physicality in the rallies, the Serb hitting 39 winners and drawing plenty of errors from his opponent's racquet.
Once Edmund fell two sets behind, history suggested a comeback - like his compatriot Dan Evans managed on Monday - was unlikely.
Edmund had never won a match after falling two sets behind - nor even claimed a setback - and suffered another straight-set defeat when Lajovic took the third-set tie-break.