Rafael Nadal missed three match points and needed medical treatment as his comeback tournament ended in a quarter-final defeat by Jordan Thompson.
Nadal looked poised to claim another straight-sets win at the Brisbane International when he brought up a first match point in the 10th game of the second set but missed a backhand overhead.
Two more chances followed in the tie-break but Nadal was unable to take either and Australian Thompson fought back to claim a 5-7 7-6 (6) 6-3 victory after three hours and 25 minutes.
More concerning was the off-court medical time-out Nadal took at 1-4 in the deciding set for treatment to his upper left leg, although he was able to continue without too much apparent discomfort.
The 37-year-old had surgery on the psoas tendon in his left hip in June after being sidelined since suffering an injury at last January’s Australian Open.
Thompson will take on second seed Grigor Dimitrov in the semi-finals, while top seed Holger Rune faces Russian Roman Safiullin.
In the women’s event, top seed Aryna Sabalenka continued to look sharp in a 6-1 6-4 victory over Daria Kasatkina, her 14th-straight win in Australia, while second seed Elena Rybakina was a set up on Anastasia Potapova when the Russian retired.
Sabalenka will take on fellow Belarusian Victoria Azarenka in the last four after she battled past Jelena Ostapenko, while Czech Linda Noskova won the battle of the teenagers against 16-year-old Mirra Andreeva.
At the ASB Classic in Auckland, defending champion Coco Gauff and second seed Elina Svitolina both eased into the semi-finals, while Alexander Zverev defeated Stefanos Tsitsipas to help Germany defeat Greece in the United Cup quarter-finals.
Meanwhile, Harriet Dart reached the biggest final of her career at the WTA 125 event in Canberra, battling to a 7-5 3-6 7-5 victory over American Katie Volynets, and Heather Watson is through to the doubles final in Brisbane with Belgian Greet Minnen.
