Nick Kyrgios has shown incredible guts and determination to fight through an injury to win at the Brisbane International.
Criticised in the past for a lack of effort, the fourth seed looked like he would inevitably retire but battled back to down fellow Australian Matthew Ebden in three sets.
World No.21 Kyrgios - ranked 55 spots higher than his countryman - had his left knee strapped in the first set and never looked comfortable but still clinched a 6-7 (7-3) 7-6 (7-5) 6-2 victory at Pat Rafter Arena.
The 22-year-old had cut short his 2017 season in October due to a hip complaint in a bid to launch a fresh tilt at the Australian Open starting on January 15.
Kyrgios - who received a Brisbane first round bye - was also hoping to turn around his poor 2017 grand slam record in which he failed to advance past the second round.
The dual grand slam quarterfinalist didn't look like lasting long in his first career meeting with Ebden after calling for a medical timeout nine games into the match.
He was noticeably limping after receiving treatment and strapping to the back of his left knee.
Two games later the end appeared nigh after Kyrgios received more treatment and had his knee covered in tape by the start of the second set.
The Australian No.1 cut a frustrated figure as he gingerly moved around the court but resisted any temptation to retire.
His tenacious approach was rewarded when he somehow outlasted Ebden in the two hour plus match and booked a quarterfinal clash with Ukraine's world No.38 Alexandr Dolgopolov.
Former Brisbane finalist Dolgopolov brushed aside Horacio Zeballos of Argentina 6-1 6-2.