The 42-year-old Swede had an 18-under 192 total on the LaCantera Golf Club Resort Course after opening with rounds of 61 and 65. He won the last of his five PGA TOUR titles in the 2001 Honda Classic.
Because of the long time since his last win, Parnevik said he had some doubts about his game even though he entered the round with a four-shot lead.
'It was tough out there, I thought, for me,' he said. 'I was not very relaxed over the shots or the putts. Now, when I haven't played that great for a while, it's a lot tougher because those bad shots seem to stick in your mind somewhere.'
Fellow Swede Mathias Gronberg was 15 under after a 65. Texan Justin Leonard, the 2000 and '01 winner, was 14 under after a 64, and Ryan Armour (64), Daniel Chopra (64), Shigeki Maruyama (65) and Chris Stroud (64) followed at 12 under.
Parnevik had six birdies, with only two of the putts from more than 10 feet.
'Jesper hit a lot of shots close to the pin,' said Gronberg, who played in the same group. 'So, the main thing for me is to go out and play like I did today.'
Parnevik led by five early with a birdie at the first. But a bogey at the second, and Gronberg's birdie putt from the fringe, cut it to three.
Both bogeyed the 10th hole, but Parnevik regained the stroke with a 2-foot putt at the 428-yard 11th, set up by a 345-yard drive down hill.
It was the first in a three-birdie string. At the 12th, Parnevik hit his 138-yard approach to 3 feet and made another birdie. That put him four ahead again.
Leonard made his second birdie in four holes, a 16-footer that was pin high at No. 11. But he missed an opportunity when his 5-foot birdie putt lipped out on 12.
Gronberg answered Parnevik's play with birdies on four of five holes, capped by a 12-footer on No. 16.
'Mathias was playing great, Justin Leonard was playing great, a lot of guys were playing great in front of me,' Parnevik said. 'I'm playing very well, but it's going to be a tough day (in the final round) -- no doubt about it.'
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