Slovenia's Kaja Juvan pulled off an early upset for her home crowd Tuesday, defeating top-seeded Petra Martic of Croatia 6-3, 6-4 in the first round of the Zavarovalnica Sava Portoroz in Portoroz, Slovenia.
Juvan saved seven of eight break points and won 22 of her 31 second-serve points (71 percent).
Second seed Yulia Putintseva of Kazakhstan, third seed Alison Riske of the U.S. and fifth seed Tamara Zidansek of Slovenia were among the first-round winners Tuesday. Ukrainian sixth seed Dayana Yastremska retired in the second set against Italy's Jasmine Paolini, and Swedish seventh seed Rebecca Peterson went down to Italy's Lucia Bronzetti 6-3, 6-3.
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Latvian No. 3 seed Jelena Ostapenko needed one hour flat to dispatch her first-round opponent, Germany's Jule Niemeier, 6-2, 6-2 in Luxembourg.
Ostapenko will meet Dutch qualifier Arianne Hartono next. In her WTA debut, Hartono earned a marathon win over German Anna-Lena Friedsam 7-6 (5), 3-6, 7-6 (4) in two hours and 39 minutes.
No. 5 seed Marketa Vondrousova of the Czech Republic also advanced, converting 7 of 9 break-point opportunities to defeat Belgium's Alison Van Uytvanck 6-2, 6-3.
--Field Level Media