"I think it's part of my character and the way I grew up playing", said Sakkari, who knocked out Venus Williams in the last eight.
But the 38-year-old third seed came unstuck in the quarter-finals, Greek world number 49 Sakkari winning 6-4 7-6 (7-2) in the WTA Premier event in San Jose.
"I was ready for the match, compared to the last times I played against her".
Between the two of them, the Williams sisters committed 68 unforced errors in their elimination games.
Mihaela Buzarnescu rallied past fourth-seeded Elise Mertens 4-6, 6-3, 6-1 on Saturday to set up a finals showdown against Maria Sakkari at the Silicon Valley Classic. She needed one hour and 43 minutes to beat Williams, and saved two set points in the second set in the process.More news: Minecraft Movie Delayed, Rob McElhenney Drops Out As Director
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In the only match that was able to be completed on a day of bad weather at the Citi Open in Washington, Andrea Petkovic upset Belinda Bencic 6-3 2-6 7-6 (10-8).
After a back and forth opening set, Buzarnescu reeled off four games in a row during the second set to take control and never looked back.
"I just played point-by-point, because anything can happen", Mertens said. The Romanian will face No. 4 seed Elise Mertens.
Svetlana Kuznetsova had taken the first set against Yulia Putintseva and Donna Vekic was leading Magda Linette 3-0 in the opening set of their encounter when rain interrupted play.
Buzarnescu, who beat Australia's Ajla Tomljanovic 6-1, 7-5, fell to Mertens in the final in Hobart in January.