Halep has had two chances to ascend to the No.1 ranking over the last two Slams.
"Honestly, I was thinking in her situation, it must be hard", Muguruza said.
Sixth-seeded Spaniard Muguruza needed only 56 minutes to capture her second title of the year and her first in a US event, taking the $522,450 top prize in the last major US Open tune-up. I don't know what to say.
In the aftermath, Kyrgios, studly, in the quarterfinals, Rafael Nadal, returning Monday to the first place in the world, had lost his service and allowed Dimitrov to take the broad, and then to pocket the first inning on a shutout in 34 minutes.
"I lost to her so many times, I figured out something was going wrong", Muguruza said. "I want to find the recipe this year".
With the win, the 23-year-old snapped a six-match losing streak against the current world No. 1, and reached her first final since Wimbledon last month.
Perhaps that had something to do with the poor showing. "I had the match on my racket and tightened up", Kyrgios said.
"I don't think I played my best tennis today", Pliskova said.More news: BMW M5 Unveiled With 600 PS, AWD and RWD
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Dimitrov capitalized on the opportunity in front of him with more strong serving in the second set. But it's still there. "I didn't have chance in the second tiebreak".
The seventh seed won 6-3 6-4 to reach the last eight for the first time, setting up a rematch of her Wimbledon quarter-final against Simona Halep.
It all came down to an empty bucket for Halep who has suffered probably her worst defeat in years. Antetokounmpo had earlier said that he would miss the tournament because of a knee injury.
Muguruza improved to 2-0 in 2017 finals and 5-3 career.
"I think I played my best match on hardcourt so far, " she said.
When it ended, Muguruza congratulated Halep and walked around the court, smiling.
The women's bracket was missing Williams, Victoria Azarenka and Maria Sharapova.
The Czech Republic's Carolina Pliskova, whom Muguruza also beat 6-3, 6-2 in the semifinals round of Premier 5, retains the No. 1 slot. Dimitrov, a Bulgarian, took advantage and won the title with his steady serve. It was a complete display of tennis from her side with all the parts working together in a smooth manner. Dimitrov said his shoulder felt heavy as he sensed the moment and served out the match.
"He's a tricky opponent. a super-experienced player", said Dimitrov. "I'm pretty confident after that win". "That's a very Nick Kyrgios thing to do". I knew that he's going to serve big, bold serves.