In an encounter featuring former Linz champions, 2008 and 2010 winner Ivanovic bested 2009 titlist Yanina Wickmayer, 62 64.
"The first set was very close until 4-2," Ivanovic said. "And then the last couple games of the first set I played much better and she made a few more errors. The second set was very close."
"I have a tough draw," Ivanovic said. "We've played a few times in the past, so I know what to expect. She's a great fighter. I expect a very tough match."
As for Stephens, after going down an early break at 2-1 in the first set against Magdalena Rybarikova, the second-seeded American surrendered just two more games the rest of the way for a 63 61 triumph.
"I arrived a little late, so I'm still a little jet-lagged from being in Asia, but overall it thought it went well and I played a good match," said Stephens, who came into this week ranked a career-high No.12.
"All in all it was a good quality match," Petkovic said. "I played really well. The only game I'm really unhappy with is the game I served for the match at 5-2 and I had two double faults. I lost my focus, my concentration. And then she started playing really well again. I don't really have any regrets from 5-3 on to 5-5. All in all I'm pretty satisfied. I moved really well and my strokes were good. Just the focus needs to be better."
"I started badly. I was very nervous," Mayr-Achleitner said. "But in the second set I played better. Then at the end, I was getting nervous again. To finish the match against No.21 in the world is not easy.
"To have belief, that's the first thing. Belief that I can win against her. She's a great player. It was a good match."