The world No.8 has had a shadow all week in the form of former Australian doubles champion-turned commentator Rennae Stubbs, who has worked with her since August past year.
Medvedev saved four break points to take a 3-2 lead in the second set before dragging the match into a decider but his opponent, who lost their previous meeting in last year's Tokyo final, was not to be denied again.
"I was sulking a bit and there are moments that I tried not to do that". But then the ball wouldn't go in, and then I would go back to being childish and stuff.
Tsurenko ultimately blasted 20 winners to go one better than her semi-final appearance in Brisbane in 2013.
As third seed, Osaka was to meet Swiss player Timea Bacsinszky in the first round. She said after the match that she didn't know how to cope once things started to go against her.
But she said her ability to win the final would help her in Melbourne. "So I think that was sort of my main problem today".
But Nishikori, who had lost nine consecutive ATP finals over 52 tournaments in almost three years, broke the Russian player's serve on four consecutive points in the final game to clinch the match in just 2 hours, 6 minutes, at Pat Rafter Arena.
"I don't know, maybe she raised her level so much that I was not ready for that".
"I was missing my shots, just not feeling the timing perfectly".
"I feel better with my serve and that I am moving well", she said. "I feel I can kind of handle every kind of pressure on court now, even when someone like Naomi is playing really strong".
Karolina Pliskova used all her big match experience as she came from a set down to overhaul Ukraine's Lesia Tsurenko and win the Brisbane International on Sunday. "I can do to like improve the situation", she said. "I felt like I was too fast on the court today (Saturday)..."