Fifth seed Luksika Kumkhum of Thailand produced the biggest upset of the L&T Mumbai Open tennis tournament yesterday by knocking out top seed Saisai Zheng of China to enter the semi-finals of the 125K WTA event.

Luksika fought back brilliantly after dropping the opening set, hitting hard and deep with her double-fisted forehand as well as backhand, besides attacking the net at opportune times, to carve out a 3-6, 6-4, 6-4 win at the Cricket Club of India.