Pliskova, who is in contention to finish world number one, continued her stranglehold over the Spaniard with a 6-2, 6-2 victory in just 62 minutes. The Czech has not dropped a set from her two games to ensure she finishes top of the White Group.
She will play her final round robin match on Thursday against winless number seven seed Jelena Ostapenko, who has been eliminated.
Even though the match against Ostapenko will be a dead rubber, Pliskova said she wanted to continue her rich vein of form.
“Maybe it’s going to have a little bit of a different atmosphere but… I don’t want to lose any of these matches I’m playing,” she told reporters after the match.
“It would be nice to win all three (matches) in the group. If I can win a few matches in a row, it will give me extra confidence.”
It was her seventh victory from nine starts over the world number two, who appeared hampered by an upper leg injury, which required strapping early in the match.
The result means Muguruza and Venus Williams, in a re-match of the Wimbledon final this year, will fight for the last semi-finals spot from the White Group when they clash on Thursday.
Cruises past Muguruza 6-2, 6-2! pic.twitter.com/Ma3T4k0Xsn
— WTA (@WTA) October 24, 2017
Muguruza said the strapping to her left thigh was “just prevention” and she lamented her performance.
“I think my tennis wasn’t there tonight. I didn’t start well,” she said, adding she was “a little bit disappointed”.
Pliskova came out firing with her trademark serve proving lethal. She had a 70 percent success rate with her first serve in the early going and relentlessly targeted Muguruza’s body.
The 25-year-old cruised through the first set in just 26 minutes and the one-sided rout continued.
Pliskova won the first five games of the second set before Muguruza saved some face by winning consecutive games.
But it wasn’t long until Pliskova deservedly sealed her spot in the final four.
Earlier, Williams revived her WTA Finals campaign with an epic three-hour, three-set victory over Ostapenko.
The 37-year-old world number five rebounded from her opening defeat to Pliskova with a marathon 7-5, 6-7 (7/3), 7-5 win over three hours and 13 minutes — just one minute shy of the record played at the Singapore Indoor Stadium.
The 37 games played was a WTA Finals tournament record.
“A win is a win. That’s all I can say,” a terse Williams told reporters after the match.
The result will sting for Ostapenko who started brightly, working Williams around the court and hitting the lines with precision, notably several piercing cross-court winners.
The 20-year-old delivered 12 of the first 13 winners in the match before her confidence nosedived as she struggled with her serve, which was broken nine times by Williams.
Ostapenko admitted problems on her serve brought about her undoing.
“I was just a little bit tight in some moments,” she said. “I fought until the last point but my serve wasn’t really amazing today.”
Simona Halep says she is relishing being the world number one after delivering an ominous warning to her rivals at the WTA Finals with a crushing, straight-sets victory over the in-form Caroline Garcia on Monday.
In her opening round robin match at the eight-player season finale, Halep halted Garcia’s 11-match winning streak with a 6-4, 6-2 masterclass in 88 minutes at the Singapore Indoor Stadium.
It was sweet revenge for the recently crowned world number one from Romania, who lost to France’s Garcia in this month’s China Open final in Beijing.
Halep, who received the top billing a day before the final in Beijing, said she enjoyed winning her first match as the world number one.
“I feel happy. I feel great winning the first match in the first tournament coming in as number one,” she told reporters after the match.
“It’s a nice thing that I can be number one at the end of the year but it is not the most important thing in this moment for me. I just want to win the matches that I’m playing here.”
Garcia, the world number eight, had secured the last spot for Singapore after winning back-to-back titles in Wuhan and Beijing, but she was thoroughly outclassed in her debut WTA Finals match.
“I’m disappointed about the loss,” Garcia said. “It was not the way I wanted but it’s not over yet.”
Halep’s famed defensive prowess and precision hitting took hold of proceedings, particularly as she breezed through the second set in 38 minutes.
In the Red Group’s second match, world number six Caroline Wozniacki posted her first win over Elina Svitolina in grand style with a 6-2, 6-0 thrashing in just 59 minutes.
Denmark’s Wozniacki had previously lost all three matches to Svitolina, including crushing finals losses in Dubai and Toronto this year, but won 10 straight games in a one-sided rout. She broke three times during a dominant second set lasting only 26 minutes.
“I just stayed really aggressive and really tried to just go for my shots,” Wozniacki told reporters after the match. “I think I just kind of broke her down a little bit. Then I think she lost the belief or she tried to go a little bit more for it.”
Svitolina, playing in her first WTA Finals match, said she struggled to adjust to the Singapore court’s slower surface.
“This court is very, very slow. Today I completely lost my rhythm after (a) couple of games,” she said. “I’m very disappointed with the performance today.”
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.
Downs Jelena Ostapenko 6-3, 6-4! pic.twitter.com/C9pcuIndqB
— WTA (@WTA) October 22, 2017
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.”
Defeats Venus Williams 6-2, 6-2! pic.twitter.com/IHG4bQx8cb
— WTA (@WTA) October 22, 2017