It took only an hour to Angelique Kerber to finally advance to the semifinals of the WTA Finals after a straight-set win against Madison Keys, who is consequentially eliminated from the competition. The German closes her performance in the first phase of the tournament with three wins and zero losses, with only one set lost in her opening match against Dominika Cibulkova and another straight-set win recorded against Simona Halep.

After dominating her previous match, always against Dominika Cibulkova, Keys couldn't make a real difference with her serve during today's performance, with a more consistent German able to take advantage of her second serve to attack and gain important points; during the entire match, Keys managed to hit 61 percent of first serves in, but she won only four points on her second serve). The more experience has probably helped the German too, against a 21-year-old Keys at her debut in Singapore.

Angelique Kerber serving en route to win against Madison Keys [Photo credit: Julian Finney/Getty Images]   
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After a long exchange of breaks, Kerber takes full control of the set

Keys started the first set with her usual dominance on serve, quickly gaining an early lead, while her opponent needed a little more effort to level off. Afer that, Kerber immediately tried to gain the lead, and an error from the American on the first break point eased her task.

The German failed to consolidate it as she performed a disastrous game on serve, with three double faults - one on break point - which gifted the break back to Keys right away. 

Similarly, a game full of errors from the 21-year-old gave the German the lead again, but one more time she couldn't consolidate it; she made too many errors trying to quickly close out points with winners and hit the fourth double fault of her match on the break point.

Another break, this time to love, gave the German the lead for the third time, and eventually, she didn't fail to consolidate it. Keys fought back, gaining one more break point, but a fateful error wasted it, and in the end, a net-cord sabotaged her forehand, giving the game to Kerber.

The hard-fought game seemed to affect the American, as Kerber didn't need to work hard to conquer the following game and the set, converting her second set point thanks to one of many forehand errors from her opponent.

Madison Keys hitting a forehand during her match against Angelique Kerber [Photo credit: Clive Brunskill/Getty Images]

Kerber fights back after a slow start and dominates the second set

A talk with her coach seemed to help Keys at the beginning of the second set, as she broke her opponent to gain an early advantage, and then played the first solid game on serve since the beginning of the match to consolidate a 2-0 lead.

From then on, however, the world number one took a decisive control of the match, leveling off the score and then holding to take the lead again, with a partial score of 12 points to 2.

The 21-year-old seemed unable to find some consistency on serve, struggling against the German's all-court defense. Despite having her chances to hold, she couldn't convert them, and two more forehand errors allowed Kerber to claim another break. The German easily held, hitting two aces to go 5-2 up.

Keys tried to react, holding her following game for the first time since the beginning of the set, but then could nothing against a Kerber fully confident with her serve. One good first serve on the first match point closed a very quick final game, giving Kerber a well-deserved win and the first place in the Red Group.

Angelique Kerber and Madison Keys meeting at the net after their match [Photo credit: Clive Brunskill/Getty Images]

In front of similar statistics in winners (14 for Kerber, 15 for Keys), a larger number of unforced errors (31, against the German's 12) heavily affected the American's performance, similarly as it happened during her opening match against Simona Halep.

Angelique Kerber will meet one between Agnieszka Radwanska and Karolina Pliskova for a place in the final round, while the second qualifier of the Red Group, Dominika Cibulkova, is already set to play White Group's winner Svetlana Kuznetsova.