Nick O'Hern was finding the going much tougher on day two of the Frys.com Open in California.
The Australian matched the course record with a nine-under par 62 to hold a three-shot lead overnight, but he struggled to make any further headway with rain and cold weather affecting the course.
Although he birdied the second hole, a bogey on the 10th dropped him back to level par midway through his round.
Nicolas Colsaerts took advantage to close up to within one shot.
Starting on the back nine, the Belgian had an indifferent start, with two bogeys to go with four birdies seeing him make the turn in 34, but steady progress along the front nine had him within one shot of O'Hern.
Jhonattan Vegas, who was level with Colsaerts on six under overnight, was among the later starters.
Several others were trying to make the most of O'Hern's slow day.
Two early birdies for Greg Owen helped him move to three-under par after 11 holes to sit just behind the leader, while Tim Herron's outstanding showing on the back nine - including an ace on the 18th - helped him gain six shots through 11 holes.
