The second seed Ana Ivanovic has withstood a stern challenge from America's Alison Riske, to progress to the second round of the Auckland tennis Classic.
The 26-year-old Serb, who won the French Open in 2008 and is currently ranked 16th in the world, won the game in a second set tie break.
Riske, ranked 57th in the worked, was no pushover, but eventually yielded 7-5 7-6.
Meanwhile, fourth seed Sorana Cirstea of Romania has been knocked out of the tournament by the unfancied Canadian qualifier Sharon Fichman.
At 22nd in the world, Cirstea provided little resistence to her 23-year-old opponent, who is ranked 116th, losing 6-1 6-4.
Earlier, 2010 champion Yanina Wickmayer was also knocked out by the Czech qualifier, Kristyna Pliskova.
Wickmayer lost the first set in a tiebreaker, before the Belgian was routed in the second, 6-0.
The 24-year-old, who was beaten in the Auckland Classic finals in 2012 and 2011, is currently ranked 51st in the world.
Pliskova, the world number 130, went on to lose to the American fifth seed Jamie Hampton in the second round.