Iga Swiatek, world number one, beat Daria Kasatkina in straight sets to make a winning start at the WTA Finals.
She has extended her winning streak against opponents ranked in the top 10 with a 6-2 6-3 victory over Kasatkina.
Swiatek saved two break points before hitting a forehand winner to take a 3-0 lead in the first set. She cruised to victory from there.
She dominated with her serve, including one on match point, and has now won all five matches against the Russian.
That is the most main draw straight-set wins recorded in a single WTA season since Serena Williams (66) and Agnieszka Radwanska (46) in 2013.
“I think I started pretty well and that gave me a lot of confidence,” Swiatek told Tennis Channel.
“But on the other hand, you have to be really careful and patient against Dasha. I wanted to play in a really solid way but put pressure on my opponent.
“I did that pretty well, and I’m happy about it.”
Swiatek, who rose to world number one in April and has won eight titles, including two Grand Slams has had.
She is the favorite to win the WTA Finals, which features eight women split into two groups. The top two finishers move into the semi-finals of the indoor tournament played on purple hard courts in Texas.
Meanwhile, French world number six Caroline Garcia, who plays Swiatek next, defeated Coco Gauff 6-4 6-3.
Garcia, 29, is making her return to the singles competition at the season-ending finals after a five-year absence.
The US Open champion is the third player to win 13 consecutive matches against top-10 ranked opponents in a single year since 2000, after Justine Henin (15 in 2007) and Venus Williams (14 in 2001).
The tournament, features the eight best players of the year, moved from usual host city Shenzhen for the second successive year.
