Coco Gauff into Auckland QF, Emma Raducanu out after falling to Elina Svitolina

AUCKLAND, New Zealand (AP)—US Open champion Coco Gauff overcame hard-hitting Czech teenager Barbara Fruhvirtova 6-3, 6-0 and extended her winning start to the year and Auckland Classic defense to the quarterfinals on Thursday.

The 16-year-old Fruhvirtova came out hitting harder than any player at the tournament so far, generating enormous power off both hands. She troubled Gauff at first and broke the American's serve to love in the third game.

Gauff immediately broke back in a game of 14 points to level at 2-2. After saving a break point in her next service game, Gauff broke again to lead 4-2.

She served for the first set and had to save a break point before clinching it in 40 minutes. Fruhvirtova tested Gauff with more high topspin but Gauff came through and finished the set with an ace.

Gauff immediately broke Fruhvirtova in the first game of the second set as she began to find more depth in her returns. She broke twice more and held serve with confidence, highlighted by a 190 kph (118 mph) ace.

Gauff had to save two break points as she served for the match at 5-0 but managed to allay any threat with her sixth ace.

Fruhvirtova came into the match with a WTA ranking of No. 117.

"She played a good match," Gauff said. "I've known her since she was 10 years old. We used be in France, training at the same academy. Her and her sister (Brenda), we grew up playing or training beside each other and it's great to see her on tour. I'm sure she's going to go even further."

Gauff will play eighth-seeded Varvara Gracheva of France in the quarterfinals on Friday. Gracheva beat Lulu Sun of Switzerland 6-3, 6-4.

Emma Raducanu's tournament ended when the 2021 US Open champion was beaten by second-seeded Elina Svitolina 6-7 (5), 7-6 (3), 6-1 in the final match of the second round.

But Raducanu will head to the Australian Open beginning on Jan. 14 confident of her fitness in her return from a nine-month injury break.

She played two marathon matches in Auckland and came through both unscathed, though she played with heavy strapping on her right thigh on Thursday. She took 2 1/2 hours to beat qualifier Elena-Gabriela Ruse in her first match.

Her match with Svitolina was the most gripping of the tournament so far and lasted almost three hours.

Raducanu led 5-2 in the first set but eventually had to take it in a tiebreaker after 71 minutes. Svitolina led early in the second set but Raducanu battled back to force a tiebreak. The Ukrainian won that set in 67 minutes.

Svitolina took a 5-0 lead in the third set and Raducanu looked fatigued at times. But she fought hard and stretched Svitolina when she served for the match at 5-1.

Seventh-seeded Petra Martic sent down six aces and converted four of nine break points on her way to beating Yuan Yue of China 6-2, 6-2. Martic will play American Emma Navarro in the quarters.