Portugal Colonial - Gauff survives tense Bencic test to reach Beijing quarter-finals

Gauff next plays either Eva Lys of Germany or fellow American McCartney Kessler in Beijing.

"It was a tough match," Gauff said. "I had chances in the first to close it out but overall I'm happy with how I fought. She was being really aggressive."

There were frustrations on both sides of the court at a largely empty stadium as the players switched between one half darkened by shade and the other in the blazing sun.

There was a flashpoint between the two players during a changeover in the second set when Switzerland's 15th seed Bencic said: "Your team is chatting. I'm too old for these mind games, okay?"

"You're the one playing the mind games," Gauff, the second seed, shot back.

The 21-year-old Gauff kept it together to win the tiebreak when Tokyo Olympic champion Bencic double-faulted on set point and threw her racquet in anger.

The world number three Gauff broke early in the third set and carried that momentum through to win when a flagging Bencic returned into the net.

With her last-16 victory, Gauff qualified for the WTA Finals in Saudi Arabia in November.

"Happy to qualify once again. Happy to be back in Riyadh and I'm glad I was able to do it here," Gauff told the on-court interviewer.

"It's been a tough tournament so far, but I'm happy to get through."

C.Cassis--PC