Serving for the title at 5-4 Sunday, Tsurenko lost 13 straight points.
Pliskova has a 3-2 lead in her overall series against Tsurenko.
The Japanese second seed has never played at the Sydney International.
Pliskova also paid tribute to her opponent, world number 27 Tsurenko, who came so close to victory.
"When you're able to turn these matches around, it gives you some extra and different confidence", Pliskova said.
Vekic broke Pliskova for an early 2-1 lead, before the former No. 1 found her stride.
"I don't know, maybe she raised her level so much that I was not ready for that".
Any hopes of Osaka repeating her quarter-final performance when she fought back from a set down against eighth-seeded Latvian Anastasija Sevastova were snuffed out in the next game. She helped me just to get motivated a little bit more, to get going a little bit more.
"This helpless feeling I have, I think today (Saturday) I learned what I have to do to, not fix it, but what I can do to improve the situation".
Of course I tried, but I felt so far away from playing good tennis.
"I don't know what really changed at 5-4", Tsurenko said. "I feel more strong now, so I can kind of handle every kind of pressure on court, even when someone like Naomi is playing really strong".
And he showed all the qualities of a top 5 player in his 66-minute demolition at the Pat Rafter Arena.
Elsewhere, Julia Goerges became the first player in 15 years to defend the Auckland Open title by coming from a set down to end the fairytale run of Canadian qualifier Bianca Andreescu.
"Physically and tennis-wise I think it was flawless".
Nishikori was runner-up to Dimitrov in 2017 and will go into Sunday's final as firm favourite against fourth-seeded Russian Daniil Medvedev, who beat Frenchman Jo-Wilfried Tsonga 7-6 (8-6), 6-2.