Updated

Auckland, New Zealand (SportsNetwork.com) - Little-known Croatian teenager Ana Konjuh stunned top-seeded Roberta Vinci on Tuesday in first-round action at the season-opening ASB Classic tennis event.

The 16-year-old wild card Konjuh rallied for a 3-6, 6-4, 6-2 win over the 30- year-old world No. 14 Vinci.

Meanwhile, former world No. 1 star Ana Ivanovic, seeded second this week, downed American Alison Riske 7-5 (7-2), 7-6 on the hardcourts at ASB Tennis Centre.

Two seeded women bowed out in straight sets, as No. 4 Sorana Cirstea, of Romania, was ousted by Canadian qualifier Sharon Fichman 6-1, 6-4 and No. 6 Lucie Safarova, of the Czech Republic, fell to Japan's Ayumi Morita 7-6 (7-2), 6-3. German Julia Goerges outlasted eighth-seeded Italian Karin Knapp in three sets, 4-6, 7-6 (7-3), 7-6 (7-2), in 2 hours, 40 minutes.

Third-seeded Belgian Kirsten Flipkens avoided the upset bug by handling Puerto Rican Monica Puig 6-4, 7-5 on Day 2.

Also winning opening-rounders were American Lauren Davis, Japanese qualifier Sachie Ishizu and Czech qualifier Kristyna Pliskova, who took out last year's Auckland runner-up, 2010 champion and 2011 runner-up Yanina Wickmayer 7-6 (7-3), 6-0. The Belgian Wickmayer lost to Polish star Agnieszka Radwanska in last year's ASB finale.