NEW YORK, NY, USA – Who is the lowest-ranked player left at the US Open? Which player’s serve has been on song? And how many hours has Madison Keys spent on court?

With the field at Flushing Meadows now whittled down to 16, wtatennis.com and SAP thought it time to go looking for answers…

320 – Keys has spent 320 minutes on court thus far – the most of any remaining player.

307 – Serena Williams’ third-round win over Johanna Larsson was her 307th at a Grand Slam tournament, overtaking Martina Navratilova for sole ownership of the Open Era record.

99 – World No.99 Lesia Tsurenko is the lowest-ranked player left in the draw, closely followed by No.92 Ana Konjuh.

85 – The percentage of first-serve points won by Serena Williams in her opening three matches – the best among the 16 players left in the draw.

50 – In 2016, no WTA player has won more matches than Angelique Kerber, who notched up number 50 by seeing off CiCi Bellis in the previous round.

36 – At 36, Venus Williams is the oldest player to reach the last 16 at a major since Martina Navratilova, then 37, at Wimbledon in 1994.

31 – Serena has unsurprisingly hit more aces, 31, than anyone else en route to the fourth round. Following closely behind is Keys with 25.

18 – Konjuh, 18, is the youngest player left in the draw. It is the third year in succession a teenager has reached the fourth round.

13 – The number of nations represented in the last 16. Countries with multiple players are USA (Keys, Serena and Venus) and the Czech Republic (Petra Kvitova, Karolina Pliskova).

12 – Kvitova has dropped fewer games, 12, than any other player en route to the fourth round.

7 – Seven of the Top 10 on the Road To Singapore leaderboard are still in contention for the US Open title: Serena, Kerber, Agnieszka Radwanska, Carla Suárez Navarro, Keys, Simona Halep and Pliskova. The only absentees are Dominika Cibulkova and Garbiñe Muguruza.

5 – An unseeded player has reached the quarterfinals at Flushing Meadows on each of the past three years. Konjuh, Anastasija Sevastova, Yaroslava Shvedova, Tsurenko and Caroline Wozniacki are all bidding to keep this run going.

4 – Madison Keys, Agnieszka Radwanska, Carla Suarez Navarro and Serena Williams have all advanced to the fourth round at all four Slams this year – the only four players to do so.

3 – Three players – Konjuh, Karolina Pliskova and Tsurenko – are through to the last 16 at a Grand Slam for the first time

1 – For the last eight years, at least one Italian has reached the US Open quarterfinals. Roberta Vinci, the 2015 runner-up, looks to make it nine when she takes on Tsurenko. The Americans have been even more dominant: 1993 was the last time a home player failed to make the last eight (Lindsay Davenport and Navratilova fell in the last 16).

0 – The number of times Shvedova has beaten Serena in four career meetings. She did famously come within a couple of games of doing so four years ago at Wimbledon.