Coco Gauff went on the offensive against Madison Keys, in her own well-measured way

NEW YORK—“Every ball, every ball, every ball,” Coco Gauff’s coach, Diego Moyano, kept telling her during her 6-2, 6-3 win over Madison Keys. “Way to compete, Coco.”

Those may not sound like words of genius. What player doesn’t try to hit every ball? What player doesn’t compete? But their constant repetition set a tone for the match that Gauff seemed to internalize. Concentration, intensity, hitting every shot with purpose, not doing anything loosely or trying to finish a point with one swing: That’s what Moyano’s words tried to communicate, and it’s how Gauff played this match from first ball to last.

Looking ahead to this all-American contest, Gauff said the key for her would be to avoid relying too heavily on her defense. Keys is the bigger hitter of the two, and it would have been tempting for the speedy and (usually) steady Gauff to sit back and wait for Keys to miss. Instead, Coco went on the offensive, but in her own well-measured way.

She mixed in a little bit of everything: Weighty down-the-line backhand drives; slice forehand approaches; sharply hooking serves down the T and into the body; and a winning defensive lob to close out the first set. Gauff has always been an instinctively savvy competitor, but in this match she showed that she’s learning the nuances of match play and how to do exactly what it takes to win the most points. If she can win one with a hard but fairly safe slice down the T, rather than going for a bomb, that’s what she’s going to do, and today it was working.

This is what you might call “forced error tennis.” How do you put your opponent in a position to lose the point, without taking on too much risk to do it? How do you induce a mistake from her, rather than try for a clean winner of your own? Gauff played that game perfectly today. She hit just seven winners, but forced Keys into 34 missed shots.

Maybe impressive, and frustrating for her opponent, was the fact that she got 49 of her 58 service returns—84 percent—back in the court. That’s a lot of free points that Keys normally wins that she wasn’t winning today. And where some players will relax after winning a first set, and get broken early in the next one, Gauff kept her nose to the grindstone and fought her way through a tough hold to start the second set. She wasn’t going to hand Keys a momentum shift.

“Every ball, every ball, every ball”—it’s a simple idea, but it takes unflagging effort to execute. Gauff will try for a repeat of that effort against Shuai Zhang on Monday.