WHAT HAPPENED: Maybe it was the close-to-midnight start of the match that threw Madison Keys off her rhythm, or the pressure of having the Round of 16 on the line. Whatever the case, the American survived a sluggish start to her match to dispatch No. 17 seed Elena Vesnina and become the fifth American woman to secure a spot in the second week at the US Open. Her 2-6, 6-4, 6-1 comeback win timed out at 1:45 a.m. ET under the roof of Arthur Ashe Stadium.

Keys found herself in a tangled mess against the doubles specialist at the beginning of the match. She played hesitant and was serving poorly, and all the while Vesnina, nearly 10 years her senior, looked calm, cool and collected. Yet as the morning wore on, the drama unfolded. As Keys put it after the match ended: "Who doesn't love a late show?" With the ever-growing support of the crowd, which saw she needed a boost, the No. 15 seed began chipping away at Vesnina's game.

"The fans were amazing," said Keys, thankful for the crowd's support. "I definitely didn't show up very well for the first set, but you guys helped me get back in the match, so thank you for staying and helping me get through that one."

Keys admitted that her nerves got the best of her early on in the match, but a little self-talk between changeovers remedied the problem.

"I think I finally just settled in," said Keys. "I was definitely nervous to start and over-amped, but then I relaxed and took a step back, and now I'm happy to be in another round."

play video Cognitive Highlight: Madison Keys - Round 3

Vesnina raced to a 3-0 lead in the first before a double fault put Keys on the board. Unfortunately for the American, it was the only time Vesnina would crack, as the Russian broke Keys a third time in the set to serve it out.

Keys secured her first lead of the match by holding in the opening game of the second set, then inched her way to 4-2 by keeping Vesnina pinned behind the baseline. When she reached her second set point on Vesnina's serve at 5-4, the diehard crowd who stuck around in Ashe were then on their feet when a forehand error from the Russian gave Keys the set and sent it to a third.

And suddenly, Keys had come alive. As Vesnina's game rapidly unraveled in the third, the Russian found it harder and harder to dig herself out of a 5-0 hole. On her second match point, a netted volley from Vesnina meant Keys would live to fight another day in Flushing Meadows.

WHAT IT MEANS: Keys' win sets up a clash with No. 4 seed Elina Svitolina in the fourth round. She has reached this stage for the third time in as many years, and she joins fellow Americans Venus Williams, Sloane Stephens, CoCo Vandeweghe and Jennifer Brady in the women's Round of 16.

The 31-year-old Vesnina has posted a career-best singles season so far, winning her third title at the BNP Paribas Open at Indian Wells, where she defeated Angelique Kerber, Venus Williams and Svetlana Kuznetsova en route to the title. She also won a doubles crown at Wimbledon and achieved a career-high ranking of No. 13. Her third-round exit denies her the chance to get to the fourth round, a stage she has never reached in her 12 attempts in New York.

MATCH POINT: Keys finished the match with 29 winners to Vesnina's 10. Does she have what it takes to top No. 4 Svitolina for her first US Open quarterfinal?

Match stats