Now that the big upsets have happened, U.S. Open fans have two questions: Who is next to fall, and when will it occur?
Goodbye, Milos Raonic. Adios, Garbine Muguruza. Later, Svetlana Kuznetsova.
MORE: Open images | Schedule | Threats in Thursday's men's matches
Will Vania King add to the list? That's one huge assignment, given her Thursday match is against No. 1 seed Serena Williams. Venus Williams also plays on Thursday, in a second-round match expected to begin about 3:30 p.m. ET.
An early match to watch: No. 5 seed Simona Halep vs. Lucie Safarova, the former a talent in search of a breakthrough, the latter a talent who has nearly as much success in major tournaments. They play at 11 a.m. ET. UPDATE: Halep won in straight sets. Other early winners included Karolina Pliskova, seeded 10th.
Weather could be a factor. Showers were expected early, possibly delaying the start of Thursday's schedule. Afternoon rain also was in the forecast.
Canada's Raonic, seeded fifth, succumb to Ryan Harrison, an American ranked No. 120 in the world.
The women's bracket was shaken when Muguruza, seeded third, was eliminated by Anastasija Sevastova of Latvia. Muguruza appeared to have breathing difficulties in a three-set first-round match and lost in straight sets.
Kuznetsova, a former Open champ seeded ninth, lost to Carolina Wozniacki 6-4, 6-4. There was a surprise within a surprise, as Wozniacki lost the first four sets before finding her stride.
“It’s not like I was playing bad,” she said. “I was actually feeling the ball pretty well. She started off on fire.
“I was running a little bit too far behind the baseline at the beginning. As the match progressed, I just tried to step in a little more.”
Someone will step in on Thursday. Maybe it will be Natalie Gulbis, who will face Germany's Laura Siegemund, the 26th seed.
Here is the schedule of women's matches at the U.S. Open.