Serena Williams has decided to shut down her 2016 season, announcing her withdrawal from the BNP Paribas WTA Finals Singapore presented by SC Global due to a shoulder injury. Serena has not played a tour-level match since losing to Karolina Pliskova in the US Open semifinals in September.

Four thoughts on Serena’s withdrawal and what it means for the WTA Finals.

1. Serena relinquishes the year-end No.1 ranking to Angelique Kerber.

Serena’s decision means there will be no battle for the year-end No.1 ranking. No.1 Angelique Kerber snapped Serena’s record-tying 186-week streak at No.1 after winning the US Open, but the German’s sub-par swing through Asia left the door open for Serena to take it back in Singapore.

With Kerber’s loss to Daria Gavrilova in the quarterfinals of the Prudential Hong Kong Tennis Open last week, the German has a 950 point lead on Serena in the rankings. Singapore offers 1500 points to the winner. Serena has won the WTA Finals the last four times she’s has played it, including back-to-back-to-back titles from 2012-2014. Kerber, by contrast, has never made it out of the round robin stage. Given their respective histories at the tournament, Singapore offered Serena a chance to finish the season where she started: at No.1.

2. Serena shuts it down early…again.

For the second straight year, Serena has shut down her season after taking a tough loss at the US Open. Given the trend, her announcement shouldn’t be a surprise. Since playing a career-high 82 matches in her astounding 2013 season, posting a 78-4 record and winning 11 titles, Serena has played fewer matches with each passing year:

2013: 82 matches, 78-4 record, won 11 titles.
2014: 60 matches, 52-8 record, won 7 titles.
2015: 56 matches, 53-3 record, won 5 titles.
2016: 36 matches, 30-6 record, win 3 titles.

Serena herself has affirmed her shift in priorities, to focus her energies on the Slams. Her win at Wimbledon this year moved her into a tie with Stefanie Graf for the Open Era record for most major titles. Healthy and rested, she’ll make her charge to break the record in 2017.

3. This decision feels different than last year.

When Serena announced last fall she would not play the Dongfeng Motor Wuhan Open, China Open, or WTA Finals, the break felt more necessary on an emotional level rather than physical. While she was struggling with elbow and knee injuries, she cited “heartbreak” as a reason too, referring to her loss to Roberta Vinci in New York that ended her historic bid for the calendar Grand Slam.

Not to discount the psychological toll this year took out of Serena as well, wherein she was trying to catch or surpass Stefanie Graf’s records for majors and consecutive weeks at No.1, but 2016 has been a particularly tough year physically. She struggled with noticeable shoulder and knee injuries during the summer hard court season and pulled out of tournaments during the clay season due to the flu.

An extended physical break to get her body teed up for the 2017 season wouldn’t be a bad thing.

4. Singapore breaks open.

Much like in 2015, Serena’s absence from the WTA Finals opens up a significant opportunity for the qualifying Elite Eight. Seven of eight qualifying spots are now confirmed, with Kerber leading the pack along with Simona Halep, defending champion Agnieszka Radwanska, Garbine Muguruza, and first-timers Karolina Pliskova, Madison Keys, and Dominika Cibulkova. The final spot will come down to either Johanna Konta, Carla Suárez Navarro, or Svetlana Kuznetsova.

The eight women represent the full range of WTA tennis, from pure power to rangy athleticism to crafty point construction. That the court at the Singapore Indoor Stadium has played like a slower hard court only neutralizes things even more. It’s no surprise that over the last two editions of the WTA Finals in Singapore, both a power-player and a counter-puncher has been represented in the final. In 2014 it was Serena defeating Halep, while last year it was Radwanska getting the better of Petra Kvitova.

Take a diverse group of the game’s best players and stick them on a neutral surface and you get a tournament that will be anything but predictable on any given day.

All photos courtesy of Getty Images.