Novak Djokovic was at a low ebb after his French Open exit, but the Serbian has experienced an incredible upturn in fortunes.
World number one Simona Halep will come up against Anastasia Pavlyuchenkova in her return from injury in Moscow.
Adrian Mannarino had gone two months with a win, but reached the second round in Moscow on Monday.
For the second consecutive year, Simona Halep will end the year as the WTA's world number one player.
Juan Martin del Potro said his latest injury blow is a "hard blow that leaves me without strength".
Elina Svitolina's absence from the WTA Tour in the coming week means Sloane Stephens is assured of a place at the WTA Finals in Singapore.
Novak Djokovic has won two grand slams this year but would rank being world number one at the end of 2018 as his greatest feat.
Ekaterina Alexandrova's impressive Linz Open form was not enough to stop Camila Giorgi from claiming the title in Austria.
After winning the Cincinnati Masters and the US Open, Novak Djokovic sealed another title at the Shanghai Masters.
Wang Qiang was unable to match Dayana Yastremska's aggressive approach and was well beaten in the WTA Hong Kong Open final.
The Hong Kong Open will feature a surprise finalist in Dayana Yastremska, with Wang Qiang beating Garbine Muguruza in the other semi-final.
A resurgent Timea Bacsinszky overcame Aryna Sabalenka to set up a Tianjin Open semi-final against Karolina Pliskova.
Kiki Bertens saw her hopes of picking up ranking points in Linz blocked by a resurgent Margarita Gasparyan on Thursday.
A quarter-final upset was on the cards when play stopped in Hong Kong, with Elina Svitolina facing defeat against Wang Qiang.
Kevin Anderson was unable to gain revenge for his defeat in the Wimbledon final, losing to an inspired Novak Djokovic in straight sets.