South Korean Chung, who reached the Australian Open semi-finals previous year, fell at the first hurdle for the second tournament in succession, going down 7-5 6-3 to a player ranked 285 places below him.
· Karolina Pliskova won her second Brisbane title, coming back from a set and 5-3 down in the second set to beat Lesia Tsurenko, 4-6, 7-5, 6-2.
Now Medvedev hit back, saving multiple break points in the early stages of the second set and breaking in the eighth game, 5-3.
Medvedev, who saw off Jo-Wilfried Tsonga in the semi-finals, saved eight break points in the second set before capitalising on an unusually errant service game from Nishikori and levelling the match.
The victory followed a semi-final performance Nishikori described as "almost perfect" and came as a relief after he lost the decider in Brisbane two years ago.
"I expected something like this before the match - I'd seen him play a couple of times and I knew it would be tough", Tsonga said.
"A lot of my time is spent in the hotel lying in bed trying to conserve as much energy as I can, because whenever I step out on court there's so much I leave out there", he said.
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Some previous rumors suggest that the third camera will be a 3D ToF sensor, but it's still all speculations for now. Two of them are vertically aligned while the third one is placed on the right under the LED flash.
"I don't really agree it was up and down because I didn't lose one serve in the match".
"I always start with this tournament and Melbourne, [but I] couldn't make it previous year".
"I was a bit more aggressive than him and it made the difference", he said.
Reigning champion Daniil Medvedev may opt to skip his Sydney International defence following a strong campaign in Brisbane.
Medvedev withstood the huge serving of Canadian Milos Raonic to win a brutal match 6-7 (2/7), 6-3, 6-4.
"I think I returned well - that was the biggest key, I think".
"The main goal is to do well in the Australian Open, but I'm really happy that I've been playing really well this week", he said.