SAN DIEGO - World No. 1 Iga Swiatek tamed China's Zheng Qinwen 6-4, 4-6, 6-1 on Thursday to ease into the quarter-finals of the San Diego Open and close in on an eighth title this season.

Swiatek, who nearly clinched an eighth trophy last week but lost in the final of the Ostrava Open in the Czech Republic, brought her form back with her to the United States where she claimed the US Open crown last month.

It will be Swiatek's 12th quarter-final of the year.

"Qinwen, she has a different game style because she's playing topspin on her forehand and the ball is flying pretty high," said Swiatek, whose seven titles include two Grand Slams the French and US Opens. "So today I had to adjust to that.

"But overall, the first matches of any tournament is about adjusting to the conditions we have here."

Coming off a first-round bye, she had the only break to take the opening set but then appeared to run out of energy and focus in the second allowing the 28th-ranked Zheng back into the match.

With seven break chances in the second, Swiatek had plenty of opportunities to bring the contest to a quick conclusion but it was big-hitting Zheng getting the timely break at 5-4 to take the second and level the match.

That provided Swiatek with a wake-up call, with Zheng holding serve to open the third before the world No. 1 ripped through the next six games to end the contest in a rout. REUTERS