Rod Laver Arena/Melbourne Park, Melbourne VIC 3000, Australia, 8 January 2016 | AAP

Bernard Tomic has upset world No.8 Kei Nishikori to reach the Brisbane International semi-finals and clinch an all-important top-16 seeding for the Australian Open.

Tomic defeated the Japanese second seed 6-3 1-6 6-3 on Friday and next faces fourth-seeded Canadian Milos Raonic for a spot in Sunday’s final.

Raonic earlier defeated France’s Lucas Pouille 6-4 6-4 in his semi at Pat Rafter Arena.

Tomic sent down nine aces in the opening set, including two on break point, before a break of his own in the eighth game allowed him to then serve it out.

It was the first time Tomic had taken a set off Nishikori after losing their past two encounters including a quarter-final defeat last year.

Japan’s 2014 US Open finalist responded in the second set, winning five straight games to level the match.

But if the Australian was rattled he didn’t show it racing to a 4-1 lead before sealing his third win of the summer on his first match-point attempt.

“That was very, very special to me,” Tomic told the Seven Network.

“Looking back, last year unfortunately I lost very comfortably to Kei and today played very different. I’ve improved so much since last year.”

Tomic will meet another top-20 player in the semis after the 14th-ranked Raonic blasted into the last four in quick fashion.

Raonic is chasing consecutive finals appearances in Brisbane after losing last year’s decider to Roger Federer, who plays Grigor Dimitrov in his quarter-final on Friday night.

For more on the Brisbane International click here.