The China women's coach and only player to win two Olympic singles titles will also be wondering which of Wang Yihan and Li Xuerui will succeed her as champion.
Just like before Li Xuerui beat Wang Xin in the semifinals on Friday, Zhang will leave her players to themselves, not play favourites, and merely wish them the best of luck.
Luck could be all that separates Wang and Li. At the start of the year, Wang Yihan was the undoubted gold-medal favourite. She'd climbed to No. 1 after winning the world title in the same arena a year ago, then added the Super Series Final title.
Nobody saw Li coming. She lost to Wang in the Malaysia Open quarterfinals in February — then didn't lose again until June. The 30-win streak included five titles and three straight wins over Wang, two in major finals. Li's form was so irresistable that China sent her to the Olympics at the last minute ahead of Wang Shixian, the Asian Games champion and former No. 1.
The no-nonsense Li hasn't dropped a game in five matches, and holds an unshakeable belief in herself.
"I started to play badminton aged around 7 1/2," she said. "I've always been strong-minded, ever since I was a little girl."
She has no fear of Wang, who has become a crowd favourite by showing her emotions on court. More than off court.
"I'm very happy to be in the final," she said. "I'm OK. Relaxed and not nervous. I'm keeping my emotions in check. It's not over yet."
China could claim the entire podium if Wang Xin beats Saina Nehwal of India in the match for bronze.
China, already assured of a second gold in two finals, will have a shot at a third in the women's doubles final.
Zhao Yunlei, who won the mixed doubles gold on Friday, will partner with Tian Qing against Mizuki Fujii and Reika Kakiiwa, who have earned Japan's first badminton medal.
Tian and Zhao combined in 2010 and won titles only when teammates Wang Xiaoli and Yu Yang didn't. When the virtually unbeatable Wang and Yu were one of four women's doubles teams disqualified this week for trying to rig the playoffs lineup, Tian and Zhao became the new favourites with their smiles and soft touch. They have a 2-1 record against the Japanese.
Russia or Canada will also win a first badminton medal when Valeria Sorokina and Nina Vislova meet Alex Bruce and Michelle Li for bronze.