Williams gains revenge
In a rematch of this year's ladies' singles final at Wimbledon, Venus Williams turned the tables on Garbine Muguruza, winning 7-5, 6-4 to reach the semi-finals in Singapore.
With both players coming into the match with a 1-1 record in the round robin stage, this was a straight shoot-out for second place in the White Group.
Just as in their meeting in Centre Court back in July, the first set was a tight affair, with the pair trading breaks before arriving at 4-4. A tie-break looked to be in the offing until Muguruza faltered when serving at 6-5 down, handing Williams two set points. While the Spaniard saved both, Williams forced another and converted to take the opener.
Muguruza responded well to that setback, moving to a 3-1 lead in the second set, but Williams recovered to 3-3 before breaking twice more to seal her passage to the semi-finals.
"I think she played very good in important moments, and I made few mistakes that I shouldn't,” Muguruza said.
“I was just trying to not get crazy and kind of wait for my opportunity. And it didn't come. In important moments, she stepped up and turned it around.”
Having beaten the Roland Garros and Wimbledon champions back to back, Williams secured second place in the White Group and qualified for the semi-finals, where she will meet the Red Group winner.
Ostapenko bows out in style
Jelena Ostapenko ended her season on a high with a 6-3, 6-1 victory over the previously undefeated Karolina Pliskova.
With Pliskova already confirmed as the White Group winner and Ostapenko eliminated, this encounter was effectively a dead rubber, but Ostapenko produced her best performance of the week to record her first victory over the Czech.
With nothing to lose, Ostapenko appeared relaxed and more comfortable with her go-for-broke style of tennis, putting in a vastly improved serving performance and ending up with 25 winners to 14 unforced errors.
The early exchanges, however, suggested that the momentum Pliskova had built up in her first two matches was still present, with the Czech forcing three break points in the first game.
Ostapenko escaped, though, and would go on to claim a crucial break of serve for a 4-3 lead. From that point on, the match ceased to be a contest, with Ostapenko's deep, precise hitting too much for Pliskova to handle.
"It was my last match here today," Ostapenko said.
"I really tried to enjoy every moment. I think I was playing quite relaxed, and I just showed my best today."
While Ostapenko - the WTA's most improved player for 2017 - ends a breakthrough year on a high, Pliskova will look to rediscover her early form in Singapore ahead of her semi-final meeting with the Red Group runner-up.