Australian third seed Nick Kyrgios overcame a leg injury to reach the quarter-finals of the Brisbane International on Wednesday as fourth seed Milos Raonic was bundled out by wildcard Alex De Minaur.

Kyrgios came back from losing the first set to fellow Australian Matthew Ebden to win 6-7 (3/7), 7-6 (7/5), 6-2, finishing the match with his leg heavily strapped.

In the late match on Pat Rafter Arena, 18-year-old De Minaur had the biggest win of his career when he stunned former champion Raonic 6-4, 6-4.

Raonic has not played since October because of calf and wrist problems and he looked rusty against De Minaur, making a host of unforced errors.

De Minaur was also able to handle the Canadian's huge serve, breaking him once in the first set then twice in the second to open a 5-2 lead.

Raonic managed to get one back as De Minaur faltered while serving for the match for the first time.

But he held his nerve on his second attempt and closed out the victory to set up a surprise quarter-final against American qualifier Michael Mmoh.

Mmoh upset Germany's eighth seed Mischa Zverev 6-2, 5-7, 6-4.

Earlier, Kyrgios took to the court with tape on the back of his left knee.

After losing the first set in a tiebreaker, the third seed had his leg heavily strapped and came back to win the next two, allaying any fears he might join the long injury list at the top of men's tennis.

"A couple of days out (from the tournament) I was playing some points with Lleyton (Hewitt) and then I kind of felt my knee a bit," he said.

"I've been kind of nursing it the last day or two but didn't really know what it was."

Kyrgios said he had some fluid on the back of his left knee but it was not a cause for concern.

"It doesn't really hurt me when I move," he said, "just when I'm kind of straightening my leg.

"I'm sure it will be fine."

World number one Rafael Nadal and second seed Andy Murray were both high-profile casualties in the men's draw.

Nadal pulled out last week while Murray withdrew on Tuesday, before he had played his first match. Both are now in doubt for the Australian Open.

Kyrgios will next play tricky Ukranian Alexandr Dolgopolov in the quarter-finals.

Dolgopolov, the 2012 runner-up to Murray, was untroubled in his 6-1, 6-2 win over Argentina's Horacio Zeballos.

"At the start of the year I’m keen to play, I have a lot of energy and that’s why I’m flying on the court," Dolgopolov said.

The world number 38 is now free of injury after battling a string of problems in 2017.

"Usually I have some problem like blisters or pains during the off-season and couldn't sustain three to four weeks of work," he said.

"This time it was quite solid. I didn't have any days off and sustained the work."

Source: AFP