NEW YORK, NY, USA – Who has enjoyed the smoothest passage to the final? What does Angelique Kerber need to do to top the rankings? And just how impressive has Serena Williams’ serving been?

These are just a few of the questions answered in a US Open semifinal edition of wtatennis.com’s By The Numbers.

439 – Karolina Pliskova’s three aces against Ana Konjuh took her tally for the year to a WTA leading 439 from 54 matches.

110 – The average rank of Pliskova’s opponent en route to the last four is 110 (No.243 Sofia Kenin, No.192 Montserrat González, No.92 Ana Konjuh, No.6 Venus Williams and No.18 Anastasia Pavlyuchenkova).

84 – Serena’s peerless delivery has helped her win 149 of 177 (84%) points on her first serve – the best percentage of any singles player this fortnight.

74 – Wozniacki is currently ranked No.74 – her lowest position since August 2007. Aside from unranked Kim Clijsters in 2009, Wozniacki is bidding to be the lowest-ranked finalist in US Open history.

60 – Serena has struck more aces, 60, than any other player in the tournament. Kerber, meanwhile, has hit just six.

52 – Kerber’s victory over Roberta Vinci in the quarterfinals was her 52nd of the year. This is the most by any player on tour (Simona Halep is her closest competition, with 40 wins).

48 – Wozniacki has won 48 of her 71 meetings with left-handers on tour. Seven of these defeats have come against Kerber, including four on hardcourts. The Dane has, however, won their only two meetings stateside, at Cincinnati (2014) and Indian Wells (2013).

34 – Williams will be aged 34 years and 350 days at the end of the tournament, making her the second-oldest US Open semifinalist in the Open Era, after Billie Jean King in 1979, who was 35 years, 291 days.

33 – Williams is appearing in her 33rd Grand Slam semifinal. For Pliskova it is her very first.

17 – In her 17 previous Grand Slam appearances Pliskova had never reached the second week. The last player to reach a major semifinal having never previously been beyond the third round was Madison Keys at the 2015 Australian Open.

10 – Wozniacki has defeated two Top 10 players (No.9 Madison Keys and No.10 Svetlana Kuznetsova) this fortnight – a feat she had never achieved in 36 previous majors.

7 – Wozniacki is the seventh unseeded player to make the US Open semifinals since the number of seeds was increased to 32 in 2001; the others were Clijsters (2009), Yanina Wickmayer (2009), Kerber (2011), Flavia Pennetta (2013), Peng Shuai (2014) and Vinci (2015).

6 – Pliskova is projected to reach a new career-high ranking of No.6 and could rise as high as No.5 by winning the title.

4 – Williams is bidding to reach all four major finals in the same year for the very first time. The last player to achieve this feat was Justine Henin in 2006.

2 – In her five matches Williams has dropped serve just twice – both coming during her quarterfinal against Halep.

1 – Williams needs to win her semifinal to have a chance of extending her 186-week stay as World No.1. If Kerber advances to the final, Williams will need to win the title to hold on to top spot.

0 – The number of sets Kerber has conceded en route to the semifinals. The last player to win a major without dropping a set was Serena at the 2014 US Open.