As a player who has been around for almost two decades, Serena Williams may find quitting the professional tennis rather hard. But, one thing is for sure, she won't get any younger even though she had the most crushing dominance over the WTA Tour once she got past the 30 years of age milestone.

Being absent from the tour for the most part of the season due to pregnancy, she gave birth to a child not long ago stirring up the debate on her possible comeback timetable. She will turn 36 in about two weeks and she made it clear earlier this year that her comeback to action must be a successful one, otherwise, she won't stick around too long.

It's a very down to earth approach for probably the best female tennis player in history. So, it might the time to inspect some of the possible candidates to replace Serena Williams.

Sloane Stephens and Madison Keys

The 24-year-old American tennis star made quite a comeback finishing the US Open Series with a first Grand Slam under her belt. Struggling with injuries over the past few years, Stephens underwent a foot surgery only to start a long and grueling recovery. She has shown some signs of her being in the zone prior to US Open. Playing three WTA events in a row, she went to reach the semis both in Cincinnati and Toronto. The 2017 US Open Tennis Championships saw Sloane Stephens riding the wave as she went on to set all-American final against Madison Keys, another resurrected player on US soil.

Keys is even younger than Stephens. Aged 22, she might be ready to aim higher than a top 10 presence after reaching her maiden Grand Slam final.

Garbine Muguruza replaced Karolina Pliskova at the summit

As the 24th world No. 1 in the WTA's history, Garbine Muguruza, 23, might be the leader of her generation. While other peers like Simona Halep or Karolina Plsikova had problems dealing with the thing air from the summit, the tennis star from Spain is showing a stronger approach.

Winning her second Grand Slam title earlier this year at Wimbledon gave her a huge boost and she is now a pillar of the women's tennis. On the other side, the 25-year-old Czech's short reign seemed to have been the sole result of overall consistency or just a glitch in the system. As the world No. 1, she should've proven her value and status at US Open by defending her result from 2016.

Instead, she only made it into the last eight stages losing to Coco Vandeweghe.

In the meantime, the younger generation means Jelena Ostapenko but the 20-year-old Latvian tennis star who went on winning the 2017 French Open is having issues to find a balance between raw power and wisdom.