WTA Finals: Garbine Muguruza beats Jelena Ostapenko; Karolina Pliskova beats Venus Williams

Karolina Pliskova needed just 72 minutes to see off Venus Williams

Garbine Muguruza and Karolina Pliskova registered straightforward victories on day one of the WTA Finals in Singapore.

Czech world number three Pliskova breezed past American Venus Williams 6-2 6-2 in the opening round-robin match.

Wimbledon champion Muguruza of Spain then beat Latvia's French Open winner Jelena Ostapenko 6-3 6-4 to join Pliskova at the top of the White Group.

The Red Group gets under way on Monday, with seven of the eight finalists able to finish the year as world number one.

Muguruza, who topped the rankings for three weeks this year, is 40 points behind current leader Simona Halep.

The Romanian will play France's Caroline Garcia in Monday's opening match at 12:30 BST, followed by Ukraine's Elina Svitolina against Caroline Wozniacki of Denmark.

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Neither Muguruza or Ostapenko settled straight away in Singapore, with Muguruza eventually consolidating her break with a love hold.

Latvia's Ostapenko won their last encounter at the Wuhan Open in September but she struggled for consistency here.

Ostapenko hit 21 winners to Muguruza's 10, but her 25 unforced errors and four double faults cost her as she pushed Muguruza in the final few games.

She forced Muguruza to wait as the Spaniard served for the set, saving three match points, but Mugurza kept calm to secure victory.

"She was playing very well at the end of the match, she was using her last opportunity and I managed to keep composed and turn it around," said Muguruza.

"I think I was fighting very well and my shots were there in the important moments. Jelena is so young and confident that I knew it was going to be difficult."

Earlier Pliskova, who was world number one for seven weeks in the summer, sped past world number eight Williams in the first match of the day.

Williams, the oldest player at this year's tournament at 37, has appeared five times at the end of season event and won the title in 2008.

The Wimbledon finalist struggled with her serve against Pliskova, hitting six double faults and making 19 unforced errors to Pliskova's 12.

However, Pliskova's consistency showed as she hit 25 winners, along with five aces, to register a speedy victory.

"I think my serve was good today, it could be better but I hit some aces," said the Czech.

"Maybe the score looks a little easier than it was. I think it was very tough."

Venus Williams returned to the top 10 this year after dropping out of the top 100 in 2011