Emma Raducanu looked below-par in an Australian Open second-round defeat by Austria's Anastasia Potapova that denied the Briton a meeting with world number one Aryna Sabalenka.
Raducanu, seeded 28th, lost 7-6 (7-3) 6-2 against 55th-ranked Potapova in Melbourne.
The British number one looked flat in her mood and movement, with mistakes coming from all parts of her game.
The 23-year-old lacked certainty in the forehand she has recently tweaked, while a wild drive volley at an important stage in the first set and a double fault to hand over a break for 4-1 in the second further added to her discomfort.
Former US Open champion Raducanu, seeded at a Grand Slam for the first time in more than three years, had her off-season disrupted by a foot injury and did not return to court for hitting sessions until 20 December.
"I want to be playing a different way, and I think the misalignment with how I'm playing right now and how I want to be playing is something I want to work on," Raducanu said.
"There are definitely pockets of me playing how I want to play and it comes out in flashes, which is a positive. But it's not how I want to be consistently every day.
"It's not going to fall into place straight away, but the more I work on how I want to be playing, it will be more of my identity every time I step onto the court.
"I need to work at that, but it's not going to happen overnight."
While Raducanu improved to beat 197th-ranked Mananchaya Sawangkaew in the first round, she looked undercooked against Potapova.
Russian-born Potapova also made a huge amount of errors in a poor-quality first set which started with five breaks of serve before Raducanu pulled away.
Raducanu served for the first set at 5-4 but was broken back by Potapova, who promptly pulled away in the tie-break.
After Potapova took a lengthy break at the end of the set, she made a fast start to the second and broke twice for a 3-0 lead.
The pair exchanged breaks before Potapova asserted her authority and cruised to victory, with a subdued Raducanu making a hasty exit.
Eyes had inevitably drawn towards the potential meeting with Sabalenka - but this loss was a sharp reminder of where Raducanu's level remains.
Meanwhile, British qualifier Arthur Fery was beaten 7-6 (7-4) 6-1 6-3 by Argentina's Tomas Martin Etcheverry in the men's second round.
BBC