Coco Gauff has come back to win her first-round match at the U.S. Open after losing a set against an opponent who frustrated her with the time she took between points. Gauff came through a 30-point, 25-plus-minute game to begin the second set and wound up beating Laura Siegemund 3-6, 6-2, 6-4. Some highly seeded players lost earlier Monday on Day 1 at the year’s last Grand Slam tournament. The No. 4 man, Holger Rune, and the No. 8 woman, Maria Sakkari, both exited.