Wimbledon champion Garbine Muguruza served warning of her intention to win both the WTA Finals and the year-end world number one crown when she crushed Jelena Ostapenko in straight sets on Sunday.
The freshly crowned WTA player of the year was far too solid for an erratic Ostapenko, winning 6-3, 6-4 in 85 minutes to open her campaign at the eight-woman season finale in Singapore.
Muguruza, who is playing her third consecutive WTA Finals and reached the last four in 2015, gained in strength to take control of her opening White Group round robin match.
The Spanish world number two stuttered at the finishing line when she was broken when serving for the match. But she regrouped to eventually serve it out in the 10th game.
Muguruza, 24, said she was pleased to overcome the late jitters. "I wanted to win so badly and she was just not giving me anything," she told reporters.
"I waited for my moment, where I served and tried to take control. It went well."
Muguruza, who was number one for four weeks until she was replaced by Simona Halep earlier this month, is one of seven players who can finish the year on top of the rankings by winning in Singapore.
Ostapenko's high-voltage game was spectacular at times, as shown by her 16 winners in the first set. But 10 unforced errors sabotaged her chances against a ruthless opponent and she never recovered.
"I'm not very pleased because I was making a lot of unforced errors and couldn't really get used to the court and feel my game," Ostapenko said.
Earlier in White Group, in the tournament's opening match, Karolina Pliskova made an explosive start when she beat 37-year-old Venus Williams 6-2, 6-2 in 73 minutes.
The Czech world number three, playing in her second consecutive WTA Finals, overwhelmed a sluggish Williams, who is back in the elite tournament for the first time since 2009.
Even though she did not make it out of the group stage a year ago, Pliskova said the experience helped enormously.
"I think I had quite an advantage from that she (Williams) was not playing for the last few years in WTA Finals," Pliskova said.
"I don't know how she felt but I think I was trying to take that advantage that I was here last year."
The match was an anti-climax for Williams and an early blow to her bid to be crowned the world's number one for the first time in 15 years.
Williams said she was confident of rebounding from the defeat. "Yeah, I have been in this position before," she said.
"I felt like I returned well today. I just didn't execute as well during the point."