Both Agnieszka Radwanska and Garbiñe Muguruza will feel that they should have a win next to their name but both players squandered match points in their first group matches with Svetlana Kuznetsova and Karolina Pliskova.
12 months ago when Radwanska won the WTA Finals in a three set match with two-time Wimbledon champion Petra Kvitova, the Pole was one of the favourites for the Australian Open the following January.
However, Radwanska reached the semifinals in Melbourne for the second time in three years but lost to former world number one Serena Williams.
Meanwhile, the French Open champion has suffered disappointment after disappointment since winning her first Grand Slam singles title in June.
Muguruza is a positive player and the Spaniard will believe that she has a chance of winning this tournament, even though she hardly has any form coming into these championships.
Radwanska's progression in Singapore so far
The defending champion was the favourite in her match with Kuznetsova as the two-time Grand Slam champion qualified for the WTA Finals at the last minute by retaining her title in Moscow, the first time she has defended a singles title in her career.
Unfortunately, the current world number three was unable to capitalise on Kuznetsova's draining flight journey, that lasted 10 and a half hours from Moscow to Singapore.
Muguruza's poor form continues
Muguruza is currently ranked at number six in the world due to her failure to defend points that she sustained last year, including a run to the final of Wimbledon but lost in the second round this year, failing to back up her French Open triumph.
The Spaniard just about qualified for Singapore, which would have been a disaster had she missed out, but though the French Open champion may be erratic at times, she is a tough fighter out there on the court and will be bitterly disappointed to have surrendered a 4-0 lead in the final set against Pliskova.
Radwanska and Muguruza have met on seven occasions and the fifth seed has a slender 4-3 advantage in their head-to-head meetings.
The Pole won their first two meetings at the Miami Open in 2012 and at the Australian Open in 2014, both in the fourth round in straight sets.
However, the Spaniard would turn the head-to-head in her favour by winning the next four consecutive encounters with the 27-year-old.
Starting with the round of 16 in Sydney in 2015, Muguruza recovered from a set down to defeat Radwanska, 3-6, 7-6 (4), 6-2 and followed this up with a straight-sets victory in Dubai.
Another three set encounter ensued in the semifinals of Wimbledon last year, and the French Open champion stunned the 2012 runner-up, 6-2, 3-6, 6-3 to advance to her first Grand Slam singles final.
Muguruza extended the lead in their rivalry by defeating Radwanska for the fourth time last year in Beijing in three sets.
Finally, there was some joy for Radwanska as she secured her third victory over Muguruza in a three set epic at the WTA Finals last year in the semifinals, 6-7 (5), 6-3, 7-5, en route to claiming the biggest title of her career.
This match is extremely close and could go either way, Radwanska is playing the better tennis out of the two players at the moment, and the Pole has the tools to get Muguruza frustrated.
The defending champion will need to get Muguruza off the baseline by throwing in some drop shots and working on the Spaniard's movement due to her ankle that had been taped during a practice session in Singapore.
However, Muguruza can literally blast Radwanska off the court if she serves well, remains aggressive on the baseline and keeps the points short as the Pole will come out on top in the majority of the long rallies.
Both players are in a precarious position in this group and can ill-afford to lose this match.
Muguruza will be eliminated from the tournament if Radwanska defeats her and Kuznetsova defeats Pliskova, and Radwanska's title defence will be over if she loses to Muguruza and Pliskova defeats Kuznetsova.
This is the second match scheduled on Centre Court following the encounter between the US Open finalist Karolina Pliskova and two-time Grand Slam champion Svetlana Kuznetsova.
There will be a lot of tension this match but if both players can replicate the matches from their semifinal encounters at Wimbledon and here in Singapore last year, then the crowd will be in for a treat.
Prediction: Muguruza in three sets