Coco Gauff insists she is not even close to achieving her full potential after the 15-year-old exited the Australian Open in tears on Sunday.
Gauff's fellow American Sofia Kenin recovered from a set down to win 6-7, 6-3, 6-0 and reach the last eight in Melbourne.
The 21-year-old now plays Ons Jabeur after the unseeded Tunisian defeated China's Wang Qiang 7-6, 6-1 to become the first Arab woman to reach a Grand Slam quarter-final.
Gauff, the youngest player in the draw, is one of the stories of the Australian Open, beating Venus Williams in the first round and then reigning champion Naomi Osaka in round three.
The 15-year-old now has to get back to school homework, blamed her loss on too many errors and said that nerves had nothing to do with it.
But she also admitted that the last few weeks had almost been too good to be true.
"I couldn't really write this, I don't think anybody could really write how this past couple months have gone," said the teenager.
"I still have so much I feel like I can get better on. Even my parents, my team, they all believe I can get better. I don't even think this is close to a peak for me, even though I'm doing well right now."
Gauff shed tears of disappointment as she trudged off court after defeat, but said that she was happy with how she dealt with the occasion.
"The thing I'm most proud of myself is how I handled it on the court," she said. "Even though today I lost a set 6-0, I was still believing I could win it."
Petra Kvitova battled back from losing the first set to overcome Maria Sakkari – and her noisy Greek fans – on Rod Laver Arena.
"When I was shaking the hand with the umpire, I told him it was like a soccer match today," Kvitova said. "It's nice on one side. On the other side, it's the tennis, and it's not a Fed Cup. It's strange. But ... it didn't bother me at all."
The Czech will now face top seed Ash Barty after the home favourite defeated Alison Riske 6-3, 1-6, 6-4.
Is there anything this man can't do?@DjokerNole in full circle 🔄
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Novak Djokovic continued his imperious progress in Melbourne negotiating a potentially tricky encounter with Diego Schwartzman 6-3, 6-4, 6-4.
"I stepped out on the court with a clear game plan what I need to do," the 32-year Serb said. "I think I kept things pretty much in control in all three sets. Maybe could have finished the match a bit earlier."
Djokovic moves on to a quarter-final meeting with Milos Raonic, who he has beaten in all nine of their previous meetings.
The Canadian defeated 2018 finalist Marin Cilic 6-4 6-3 7-5 to secure his latest clash with Djokovic.
Roger Federer recovered from a slow start against Marton Fucsovics to beat the Hungarian Hungarian 4-6, 6-1, 6-2, 6-2.
The six-time Australian Open winner, who was two points from defeat against John Millman in his previous round, looked rusty in the first set with Fucsovics breaking him in the seventh game to win the set.
But the 38-year-old Swiss, a 20-times Grand Slam winner, soon shifted up a gear and broke Fucsovics early in each of the next three sets to reach the quarter-finals for the 15th time.
Federer will now face American Tennys Sandgren, who defeated No 12 seed Fabio Fognini 7-6, 7-5 6-7, 6-4 earlier on Sunday.
