India, Sept. 8 -- On match point, Coco Gauff tried something different. The 22-year-old American is a defensive baseliner who clings to the back of the court to build points. Now, when she was a point away from a spot in the last eight of a Grand Slam, she decided to serve-and-volley for the first time in the match.

"I was thinking when I hit the serve that I'm either going to love this or regret this," she said in the post-match press conference. "I don't know if it shows how confident I am, or just the ideas in my head that pop up on match point."

It was probably one of those drastic ideas that comes up only when a player is hitting the ball sweetly, moving around the court with ease, pulling off moves she tends not to use, and is pla...