Karolina Pliskova said she could feel Garbine Muguruza's nerves during her win over the Spaniard at the WTA Finals.
Pliskova rallied for a 6-2 6-7 (4-7) 7-5 victory over Muguruza in the White Group in Singapore on Monday.
The Czech had trailed 4-0 in the third set and had to save a match point on her way to victory.
"Always my serve is my biggest weapon so that's the most important shot in my game," Pliskova said.
"I saw that she was a little bit nervous and missing a few shots from the baseline so I was just waiting for my chance and waiting for her mistakes."
Next up for US Open runner-up Pliskova is a clash against Svetlana Kuznetsova on Wednesday, with the Russian having also saved a match point in beating Agnieszka Radwanska.
Pliskova won the only previous meeting between the pair and knows fatigue will play a part.
She said: "It's going to be another difficult match.
"She won from [facing] match point as well today so she's going to be tired, me too, so let's see who is going to win.
"But I'm excited to play in my next match here."