Sloane Stephens knocked out the player who was embroiled in a racket-throwing controversy at the ASB Classic in Auckland.
The American ended Naomi Broady's impressive run in New Zealand on Thursday with a 7-6 (6), 6-3 win to advance to the semifinals.
But the 4-6, 7-6(4), 7-5 win over Ostapenko was marred by controversy as Broady unsuccessfully called for the Latvian to be disqualified for throwing away her racket -- which struck a ball boy -- in the second set tie-break.
British No.1 Andy Murray and his mother Judy led the support for Broady on social media following her victory over the world No.84, while French duo Alize Cornet and Kristina Mladenovic also took to Twitter to give their backing.
What a great start to the year for @NaomiBroady 👍 one of the nicest women you will meet! totally right to stick up for yourself today too!
— Andy Murray (@andy_murray) January 6, 2016
The Briton's clash with Stephens was far less dramatic. In a tight first set Broady twice had chances to win it, having recovered from 0-40 to lead 6-5 before Stephens held serve to take the set into a tie-break.
Stephens saved set point in the breaker before eventually sealing it 8-6 to take the opening set. The 22-year-old saw her serve broken early in the second set but recovered to win four successive games for a 5-2 lead.
And, despite late pressure from Broady, Stephens held out to seal the match with a cross-court backhand.
After the match Stephens paid tribute to her opponent. She said: "It was a tough one. Naomi's a great player. She has had such a great week here."