American crowd favorite Sloane Stephens was a first-round winner Monday at the New Haven Open, a final U.S. Open tune-up.

The sixth-seeded Stephens got past Slovakian qualifier Anna Schmiedlova 6-4, 6-4 on the hardcourts at the Connecticut Tennis Center at Yale University.

Day-2 upsets came when nifty Spaniard Carla Suarez Navarro took out fifth- seeded Italian Roberta Vinci 7-5, 6-3 and Czech veteran Klara Zakopalova doused eighth-seeded Slovak Dominika Cibulkova 3-6, 6-3, 6-3.

Surging Romanian Simona Halep continued her recent winning ways with a 6-2, 6-1 pasting of wild card and fading Slovak Daniela Hantuchova. Halep has captured no less than three WTA titles over the last couple of months.

Also advancing were Russians Elena Vesnina, Ekaterina Makarova and Anastasia Pavlyuchenkova, and German wild card Julia Goerges. Vesnina was the 2009 New Haven runner-up to Caroline Wozniacki.

Former French Open runner-up Sara Errani is the top seed this week and will face Makarova in the round of 16.

This week's winner will earn $117,000.