It would have been understandable if Coco Gauff had come out flat, deflated by a loss the previous evening on tennis’s biggest court — a match memorable less for the thumping final score than for Gauff’s tears and the comfort she received from her opponent, top-ranked Naomi Osaka.

But nothing is normal about Gauff, the preternatural teenager who has held sway over the United States Open, just as she did at Wimbledon in July.

On a warm Sunday afternoon at Louis Armstrong Stadium, Gauff once again held court. This time, though, it was a doubles match. Gauff, 15, and her partner, 17-year-old Caty McNally, who is deeply talented and full of promise in her own right, faced the veteran ninth-seeded tandem of Nicole Melichar and Kveta Peschke.

Instead of looking pressured and uncertain in the way she did against Osaka, Gauff looked crisp and clear, buoyed by the confidence of playing alongside a longtime friend.