Defending champion Tiger Woods returned to action this week and showed some rust at Torrey Pines, both off the tee and on the putting surface.
'I felt like I just hung in there,' said Woods, a two-time winner of this event. 'I didn't play well, but I just hung in there and kept myself out of trouble.'
The top-ranked player in the world missed the fairway off the tee on several occasions and when he gave himself opportunity for birdie, his putter let him down.
Woods played the South Course, which is rotated with the North Course over the first two rounds, and opened with two birdies and a bogey over his first nine holes, but had a few birdie chances that failed to find the bottom of the cup.
The 28-year-old missed a 12-foot putt for par at the second, his 11th, to fall back to even-par but recovered at the par-5 sixth after his second shot stopped within 18 feet of the hole.
Woods two-putted for a birdie en route to a round of 1-under-par 71.
'Just trying to get back in the competitive flow,' said Woods. 'It took a few holes to get back into it and from there, trying to basically keep myself out of trouble. This golf course can definitely put you in a pretty good hurt, and could put you behind.'
Stadler, who is making only his fifth start on the PGA Tour, played the North Course and ran off four birdies on the front side to make the turn at 4 under.
At the par-4 11th, Stadler dropped his approach inside 20 feet and drained the putt for a birdie.
He two-putted for a birdie at the par-5 14th, but stumbled with a bogey at the very next hole.
Stadler, whose father won this event in 1994, picked up steam on the closing holes, however, and knocked a 6-iron inside three feet at the par-3 17th to reach 6 under.
At the par-5 last, Stadler played his second shot to 12 feet and converted the eagle putt to secure the outright lead.
'I've been playing well, but I would never have dreamed of this today,' said Stadler. 'Even an hour ago, I wouldn't have thought about sitting here. Still don't really know what I'm doing sitting here.'
Stadler will play the South Course on Friday, the sight of his victory at the 1997 Junior World Amateur.
'It's a completely new golf course now,' said the 24-year-old. 'Still feel comfortable walking out there knowing I've been there so many times. A lot of tee shots are still similar. But it's a different course now that it was then.'
Parnevik, who is off to a good start in 2004 with a pair of top-10 finishes, also played the North Course and, like Stadler, picked up four birdies over his first nine holes.
He added a birdie at the 14th and made it two in a row with a birdie at the 15th after his approach stopped within five feet of the hole.
Parnevik was on in two at the last and took two putts for a birdie to complete a bogey-free round.
'I played very solid,' said Parnevik. 'This is probably the best I've played so far this year.'
Purdy tallied seven birdies and no bogeys on the North Course for his share of second.
'The North Course is the course you need to get, because I'm going to the U.S. Open tomorrow,' Purdy said of the South Course, which will host the U.S. Open in 2008. 'If I can shoot under par tomorrow, the other side, that's tough.'
Bob Tway, who won this event in 1986, joined Tom Lehman, Kevin Sutherland, Craig Barlow and Mathias Gronberg in a tie for fourth place at 6-under-par 66.
U.S. Ryder Cup captain Hal Sutton posted the best score at the South Course on Thursday. Sutton carded a 5-under-par 67 to finish alongside Sergio Garcia, Joey Sindelar, Tim Petrovic, Chris Riley, Steve Flesch, Heath Slocum, Fredrik Jacobson and Rich Barcelo in a tie for ninth.
Vijay Singh, who is looking to continue his streak of top-10 finishes, collected four birdies and three bogeys on the North Course to join Woods in a group at 1-under par.