Making her fourth start since returning from disk injuries in her back and neck, the 37-year-old Swede outlasted 62nd-seeded Katherine Hull in 20 holes Thursday in hazy and humid conditions at Wykagyl Country Club.
'It's key for me to just get to play and the more holes the better,' said Sorenstam, seeded third in the 64-player event. 'It's good for me to really get some pressure on myself again. I really haven't had that this year because I really haven't been in contention or I just haven't even played.'
All square after 12 holes, Sorenstam and Hull each won three of the final six holes of regulation. Sorenstam took the 219-yard 13th with a par and won the 16th and 17th with birdies, while the Australian won 14, 15 and 18 with birdies.
'It was a thriller. There was a lot of drama,' said Sorenstam, a stroke-play winner at Wykagyl in 1998 and 2000.
After halving the first extra hole with a par, Sorenstam won the match with a conceded par on the par-4 second. Hull made a double bogey, hitting into two bunkers.
'I'm just going to keep giving myself opportunities and keep working hard,' Hull said. 'I think I can compete out here and win tournaments.'
Top-seeded Lorena Ochoa easily advanced, while No. 2 Karrie Webb, major winners Cristie Kerr and Morgan Pressel and 2006 winner Brittany Lincicome were eliminated.
Ochoa, the 2006 Sybase Classic winner at Wykagyl, routed South African teenager Ashleigh Simon 6 and 5, matching the largest margin of victory in the three-year history of the event.
'It was a good day,' Ochoa said. 'In match play, it's always important to get off to a good start. ... I hope to keep going the same the next few days.'
Charlotte Mayorkas, at No. 63 the highest seed to advance in tournament history, beat Webb with a birdie on No. 18. Down three holes after five, Mayorkas tied Webb with a birdie on No. 12.
'You've just got to stay focused,' Mayorkas said. 'Even though you're down, you've just got to keep going with it.'
The fourth-seeded Kerr, the U.S. Women's Open champion, dropped a 5-and-4 decision to 61st-seeded Amy Hung, while 59th-seeded Birdie Kim again got the best of the sixth-seeded Pressel, beating the Kraft Nabisco winner 2-up. Two years ago, Kim holed out from a bunker to beat Pressel in the U.S. Women's Open.
'I just played terrible,' Pressel said.
Lincicome, seeded 13th, lost 4 and 3 to longtime European Solheim Cup standout Carin Koch, while LPGA Championship winner Suzann Pettersen, the No. 7 seed, advanced with a 19-hole victory over In-Bee Park.
'I'm happy that I played decent,' Lincicome said. 'I didn't just give it to her completely. She was making 5-footers to save par, and 20-footers like they were nothing. She just had a great day. You can't take anything away from her.'
Koch, seeded 52nd, saved par on the par-4 14th after driving into a concession stand and ended the match on 15 with another up-and-down par after a poor drive.
'We were both struggling a little bit off the tee,' Koch said. 'I managed to get it up and down a few times and made some really clutch putts.'
In other upsets, 56th-seeded Hye Jung Choi beat ninth-seeded Juli Inkster 4 and 3, and 54th-seeded Janice Moodie edged 11th-seeded Ji-Yai Shin in 19 holes.
'I played poorly,' said Inkster, a finalist last year. 'She played very well and was very consistent. I got what I deserved.'
Ochoa, the tour leader with three victories this year, will face local favorite Meaghan Francella -- a 2-and-1 winner over Meena Lee -- on Friday and could meet eighth-seeded Paula Creamer in the quarterfinals.
'The greens, even though they had rain yesterday, were a lot faster today than they were in the pro-am,' Ochoa said. 'I think I did a really good job with the speed on the greens. That's going to be a key this week.'
Creamer beat Giulia Sergas 4 and 3.
'I worked on my swing a lot this year, so it was good to go out and play competitively,' said Creamer, the 2005 Sybase winner at Wykagyl.
Fifth-seeded Se Ri Pak, coming off her fifth Jamie Farr Owens Corning Classic victory Sunday, beat Beth Bader 2-up to set up a second-round match against Christina Kim, a 3-and-2 winner over U.S. Solheim Cup partner Natalie Gulbis.