Lindsay Davenport defeated fellow American big-hitter Venus Williams 7-5 6-4 in a thrilling match to reach the quarter-finals of the US Open.
The 1998 champion was at her best in a tight battle, converting her fourth break point to go 6-5 up in the opening set as Williams sent her forehand long.
The 28-year-old fifth seed grabbed an early break in the second but had to hold off a battling Williams to win.
Williams saved four match points before Davenport snuffed out her challenge.
The fifth seed's nerve was tested as the pair traded pounding groundstrokes in a dramatic 10th game.
Davenport dug deep to save five break points and deny Williams, who has never failed to reach at least a US Open semi-final before.
"I wanted to win so badly and I played such a calm match until a few errors crept in," said Davenport.
"I didn't play the greatest game at the end but to still come and win is pretty exciting."
The 28-year-old now meets Japan's Shinobu Asagoe after she continued her impressive run at Flushing Meadows.
The unseeded player upset Greek 29th seed Eleni Daniilidou to reach the last eight.
Asagoe took a tight first-set tie-break 7-6 but could not stop Daniilidou levelling the match as she took the second 6-4.
The 28-year-old regained control to race to a 5-0 lead in the decider before faltering to let the Greek steal three games.
But the unseeded player held her nerve and served out for the match 6-3.
"I'm not really satisfied right now," said Asagoe. "I have to go further
The world number 62 is the lowest-ranked quarter-finallist since Venus Williams - then 66th in the world - in 1997.