The Japanese world No.9 rallied from 1-4 down in the second set to topple the Bulgarian 7-5 7-5 in a rematch of the 2017 final. The tournament's second seed will play France's Jeremy Chardy in Saturday's semi-final, after Nick Kyrgios's conqueror prevailed in a third set tie-break against Japan's Yasutaka Uchiyama earlier in the day.
Nishikori missed last year's Australian swing with a wrist injury but has hit the ground running in 2019. World No.4 in 2015, the lightning-fast talent has bounced out and back in the world's top 20 since but feels the latest upward swing hasn't peaked yet.
Being an Australian Open favourite may not sit well with Japan's Naomi Osaka. But the US Open champion better get used to it after admitting she gained the confidence boost she needed before the year's opening grand slam with a stirring Brisbane International quarter-final victory.
Whether she likes it or not, world No.5 Osaka moved to second in Australian Open betting behind Serena Williams after pulling off a stunning three-set comeback win over eighth-seeded Latvian Anastasija Sevastova in Brisbane.
The second seed was the first woman into the Brisbane semis. She also promptly became one of the first players tipped to lift the 2019 grand slam crown in Melbourne.
Told by media that she was considered in the mix to add to her grand slam tally later this month, the modest 21-year-old Osaka simply said: "Oh okay, that's new."
