Angelique Kerber entered the 2017 U.S Open [VIDEO] as the defending champion at the event after defeating Karolina Pliskova in the final of the 2016 US Open. However, Kerber is a first-round casualty at this year's event, losing to Naomi Osaka on Tuesday 6-3, 6-1. The result ends a poor year of Grand Slam tournaments for Kerber and it will send her crashing down the rankings when they update in just under two weeks' time.

Just a bad day or a bad year?

Kerber seemed to be focused on the individual match instead of the year as a whole when she did her post-match interview. "I think, yeah, it was not my day, completely not my day today," Kerber told ESPN after the match.

However, the loss in the broader context may not be as stunning as some suggest. Kerber also went out in the first round of the 2017 French Open earlier this year. Her highlights in majors in 2017 include a pair of fourth-round appearances at Wimbledon and at the Australian Open. That's a poor follow-up to the two titles she had won in 2016 during her Grand Slam season, titles that were added to her Wimbledon runnerup that year.

Kerber referenced the contrast between her results from 2016 and 2017. "I'm still the same player and the same person, so I think it's just -- yeah, I think it's just the matches and how I played last year from the beginning and how I'm struggling this year," Kerber said.

Kerber outside of top ten in two weeks

Kerber will lose almost all of the 2,000 ranking points that she had banked for the last year as a result of her first-round loss.

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That should see her slide outside of the top ten on tour when the rankings are updated. She doesn't have any active titles despite the fact that she still spent a large part of 2016 as the World No. 1 player. However, one notable result that she has to defend between now and the end of the year is her runner-up finish at last year's Singapore event. In truth, unless she elevates her play during the few key tournaments to be played between now and year's end Kerber, who will turn 30 in January 2018, is unlikely to make the year-end event this season.

Kerber was among the casualties in New York on Tuesday. Women's singles matches that were completed on Tuesday were not numerous, thanks to the rainy conditions. However, Pliskova, Jelena Ostapenko, and Madison Keys advanced in matches that were played in Arthur Ashe Stadium. The order of the play for Wednesday will be full as the tournament will have to scramble to try to get back on schedule.