Serena Williams’ absence from the WTA Finals in Singapore provides the eight women competing with a golden opportunity to claim the fifth-biggest trophy on the tennis calendar. Any one of them is capable of winning, but after a hard-fought, energy-sapping season, some are better placed than others to emerge victorious at the end of the week.

Garbine Muguruza won the China Open and reached the final of the Wuhan Open, so she goes into the tournament as the player most in form. The Spaniard is also a rapidly improving player, with a developing game that combines enough power and variety to overwhelm almost any opponent - if she is on her game. Given the relative lack of form of some of the other women in the draw, and the fact she has been drawn in the easier of the two groups, Muguruza should arguably be considered the slight favorite.

As the world No. 2, Simona Halep is the nominal favourite to win. She has beaten Muguruza, Flavia Pennetta, Angelique Kerber, and Agnieszka Radwanska this year. Her solitary loss against one of her fellow competitors came in the US Open semifinal against an inspired Pennetta. She has also beaten Petra Kvitova in both their previous meetings, and she boasts a 3-1 winning record over Lucie Safarova. In fact, the only woman she really has any reason to fear is Maria Sharapova, who has beaten her in all of their five past matches. Despite all that, facing Sharapova, Pennetta, and Radwanska in the group stage could prove to be a very tough task.

It is difficult to know what to expect from Petra Kvitova. In some tournaments, she strolls through the draw with ease, and in others she loses tamely to opponents she ought to beat. Some of those losses in 2015 could be partly attributed to her struggles with glandular fever, but they are not a new phenomenon – the Czech has been inconsistent for years. Nevertheless, if she plays well, Kvitova’s big serve and strong, clean groundstrokes will give her an excellent chance of emerging from her group and going on to win the WTA Finals.

It is even more challenging to predict how Maria Sharapova will perform in Singapore this week. The Russian superstar had a good year up to and including Wimbledon, but she has not completed a single match since then. She is capable of hitting form straight away, but she could just as easily lose her first two matches and be out of the tournament before she finds any kind of rhythm. Everyone involved in tennis knows about Sharapova’s superb shot-making ability and champion’s mentality, but can she really be expected to win when she has not any match practice?

Agnieszka Radwanska has been very impressive during the Asian swing, winning tournaments in Tokyo and Tianjin and reaching the semifinals in Beijing to book her place in Singapore, so she should be full of confidence in her game going into the WTA Finals. However, while the Pole’s clever tennis bamboozles most lower-ranked opponents and consistently preserves her place among the elite, it is traditionally less effective against top-10 opponents. In 2015, she has lost her only matches against Halep and Kvitova, and one of her two encounters with Kerber. Worst of all, she has lost all four of her matches against Muguruza this year, so she will be delighted the Spaniard is not in her group and will also hope to avoid her later on.

What a year it has been for Kerber. If she wins twice in Singapore, she will have won more matches than anyone else in 2015, and if she takes home the title, she will also have won more tournaments than anyone else this year. (She is currently tied at five with Serena.) The German has recorded impressive wins over Muguruza, Sharapova, and Radwanska, as well as several other top-20 players. Her stellar year speaks volumes about her consistency, but it is still difficult to imagine her lifting the trophy on November 1. Kerber simply does not seem to possess enough shot-making capability to take down other top 10 players when they are at their very best. She also typically struggles to produce her finest tennis at crucial moments against the elite, and both of those shortcomings will probably prove particularly problematic in the WTA Finals, especially since she has both Muguruza and Kvitova in her group.

Kerber is not the biggest outsider for the title, however. That dubious honor belongs to Lucie Safarova, whose year has gone rapidly downhill since her superb run to the French Open final in early June. Considering the Czech has only won nine matches since then, she can count herself very lucky to have qualified for the WTA Finals, particularly with Timea Bacsinzsky and Venus Williams so close behind her in the standings. Safarova is a good player, but there are least six players better than her in the draw, and the seventh – Kerber – is in much better form, so she will probably lose all three of her group matches.

An exciting week awaits WTA fans, and the tournament promises to be highly unpredictable.