Eighth seed Sloane Stephens won through to the Hobart International semi-finals after beating fellow American Lauren Davis 6-3 4-6 7-5.
In a marathon match that lasted over two and a half hours on Thursday, Stephens outlasted qualifier Davis to claim a memorable win.
Stephens, 19, began the match brightly and claimed three breaks on her way to taking the set 6-3.
However Davis came out firing in the second and saved five break points and claimed two of her own to win the set 6-4.
The final set was a gripping affair with both players trading blows before Stephens, who had eight aces for the match, finally overcame her compatriot 7-5 to claim a semi-final berth.
Kirsten Flipkens also needed three sets to get past Monica Niculescu 2-6 6-4 6-0.
Romania's Niculescu was far too good for her Belgian counterpart in the first set as she breezed through it 6-2.
But Flipkens stormed back into the match, clinching a tight second set before demolishing Niculescu in the third, hitting two aces and claiming three breaks.
In the day's other matches, Mona Barthel of Germany recorded a 6-3 6-3 win over Bulgaria's Tsvetana Pironkova in little over an hour while Australia's Jarmila Gajdosova was dispatched by Russian Elena Vesnina 6-3 6-2.
Vesnina will now face Stephens on Friday afternoon with Barthel to play Flipkens in the other semi-final in the night session.