# Sloane Stephens
After tasting her first Grand Slam success at the US Open in 2017, Stephens grabbed her second biggest win at the Miami open earlier this year and broke into the Top-10 for the first time in her career. She was the runner-up in the French Open and in the ensuing process was ranked in the Top-5 and reached a career high ranking of Number 3 in July. Since then she has tasted limited success barring a runner-up finish in Montreal. However her clean hitting and powerful groundstrokes makes her a definite contender for the WTA crown.
# Karolina Pliskova
Karolina Pliskova's 3882 aces this year so far are the highest among all Women competing in the WTA Finals. Since reaching her maiden Grand Slam final at the 2016 US open, Pliskova rose to World Number 1 and later relinquished that position. She hasn't reached a Grand Slam final after that and there is a feeling that her true potential hasn't been unlocked yet. Her two titles in 2018 came at the indoor clay in Stuttgart and at the Tokyo open in Japan. The addition of Grand Slam winners Rennae Stubbs and Conchita Martinez to her coaching crew seems to have helped her evolve into a more complete player. Her strong service and aggressive strokeplay will make her one to watch out for this week.