Serena Williams -- the record 22-time grand slam champion -- continues to nurse a shoulder injury
, Maria Sharapova is serving a drug suspension, Victoria Azarenka is pregnant and Petra Kvitova just didn't do enough to qualify.
That may not equate to the tournament, which begins Sunday, being wide open but each of the seven confirmed qualifiers involved -- Svetlana Kuznetsova needs to win the Kremlin Cup to deny Johanna Konta the eighth spot -- has a realistic opportunity of advancing past the round robin stage.
Given she is the world No. 1, Angelique Kerber must be the favorite, despite a swoon since replacing Williams atop the standings.
Here's a closer look at the seven confirmed players, beginning with the lone female this year to win two majors. If Konta secures the eighth spot there will be four debutantes at this year's finale.
Angelique Kerber: By winning those two grand slam titles, those who would make Kerber player of the year regardless of what happens in Singapore have a strong case. The left-handed German decided to infuse aggression into her counter-punching style in the off-season and it paid instant dividends: The 28-year-old toppled Williams in January's dramatic Australian Open final.
Injuries and dealing with the pressure of being a grand slam winner took their toll for a while, but Kerber recovered by reaching the Wimbledon final -- falling to Williams in a fine duel -- and winning the US Open two days after securing the No. 1 ranking.
The WTA Finals mark a significant test for Kerber, given that in three previous appearances she has never made it past the group stage, posting a 2-7 record.
How the year could have turned out differently had Kerber not saved a match point against Misaki Doi in the first round of the Australian Open.
Garbine Muguruza: Muguruza threatened to win a grand slam title prior to 2016 -- ousted by Williams in the 2015 Wimbledon final -- and duly prevailed at the French Open by defeating the younger Williams sister. Her hard-hitting game from the baseline can overpower almost anyone when the Spaniard is in form.
Unfortunately for the Venezuelan-born Muguruza, it hasn't happened a whole lot since Roland Garros. Since the French Open through early October, the 23-year-old compiled a mediocre 10-8 record. All eight defeats came to players lower ranked.
Agnieszka Radwanska: A tactician who eschews power for finesse and placement, Radwanska has been voted Fan Favorite by the public five times in a row, as revealed by the WTA.
For much of last year, it looked like Radwanska wouldn't qualify for the 2015 edition. Yet the 27-year-old Pole earned a spot thanks to a late flourish and then won the title
, becoming the first player since Amelie Mauresmo in 2005 to take the crown without yet capturing a grand slam.
Radwanska still hasn't won a major but she qualified for Singapore this year with plenty of room to spare.
Simona Halep: On the subject of popular players, Halep has been the most clicked player on the WTA's website the past two seasons.
One of tennis' top movers with a penchant for winning highlight-reel rallies -- similar to Radwanska -- the Romanian started the season with an underwhelming 3-5 record.
The 25-year-old gained momentum in March in Indian Wells and won a big title on clay in Madrid in May, although she has been at her most consistent since the end of June.
Halep lost the 2014 final to Williams 6-3 6-0 -- but did hand the American one of the worst losses of her career in the round-robin portion, prevailing 6-0 6-2.
New to the WTA Finals
Karolina Pliskova: Not only is Pliskova the runaway leader in aces on the women's tour with 508, but her average per match exceeds that of Williams.
The 6-foot-1 Czech established herself on the tour the previous two seasons, finishing at 24th in 2014 and 11th last year but only made her first grand slam quarterfinal at this year's US Open.
The 24-year-old did it, though, with a bang, saving a match point to beat Venus Williams before eliminating Serena in the semifinals.
Pliskova so nearly downed Kerber in the final, too, holding a break advantage in the third set.
Pliskova is the sole representative from the Czech Republic after Kvitova failed to qualify for the first time since 2010.
Madison Keys: Labeled as the next big thing in US tennis, Keys enjoyed a consistent season.
The 21-year-old American didn't make the semifinals of a major -- unlike in 2015 -- but was solid nonetheless, reaching the fourth round at all four of the grand slams.
Away from the grand slams, her booming serve and forehand propelled Keys to prestigious finals in Rome and Montreal; she also won the second title of her career in Birmingham.
The year could have been even better if not for a lingering adductor injury that affected Keys at the Australian Open. Then at Wimbledon, leg cramps surfaced in a defeat to Halep.
Dominika Cibulkova: Listed at 5-foot-3, Cibulkova isn't one of tennis' taller players. And nowadays it seems like tall power players are the norm in the women's game.
But don't let the Slovakian's height fool you. She is able to generate great pace off both the forehand and backhand and is one of the tour's top competitors.
Cibulkova only advanced to one grand slam quarterfinal -- at Wimbledon days before she got married -- but picked up plenty of points at WTA tournaments, winning three titles and reaching three other finals.
The 27-year-old is a former grand slam finalist, having made the Australian Open finale in 2014.