She then clawed her way back from a 1-4 deficit, with Muguruza -appearing exhausted and out of ideas by the end of the match - losing her final service game with two unforced errors. "I think the difference was a couple of points".
Yastremsky never won a player of the top 25, but today 18-year-old inhabitant of Odessa was simply unstoppable.
She said she knew little about the 102-ranked Yastremska, who powered to a 7-5, 6-4 victory over Zhang to reach her first WTA Tour final. Her best previous result was reaching the 2017 Istanbul quarterfinals.
"I was nervous from the first ball", Yastremska said.
"Daria played very well, but I was able to focus on each point at a time, and gave a good performance to get the win", said Zhang.
Svitolina remains in the hunt for WTA Finals qualification despite her quarter-final exit.
Wang, the world No. 24, grabbed headlines at the French Open with her straight-sets demolition of Venus Williams, offering a hint of what was to come, and later overcame Karolina Pliskova in both Beijing and Wuhan. Yastremska's win prevented the 24th-ranked Wang from winning her third career title.
Next up for the Czech is second-seeded Frenchwoman Caroline Garcia, who beat Taiwanese No. 5 seed Su-Wei Hsieh 6-3, 6-4 in the other semifinal.
"I was feeling it and my legs were a bit exhausted but I'm kind of used to it and this wasn't the reason I lost".
Svitolina, who is now looking for a tournament wild card to boost her Singapore chances, is also in the hunt for a new fitness and main coach for next season.
Natalia Medvedeva first singles trophy was taken on the eve of his 19th birthday in 1990, still under the flag of the USSR.