Lee Janzen had a piece of the lead with one hole to play on the Sunrise Course at Mirasol but the two-time U.S. Open champion bogeyed the 18th for a 72 to finish alongside Pat Perez at 11-under-par 205. Joe Ogilvie followed at 10- under-par 206.
The Australian countered with a birdie at the ninth and made it two in a row with a birdie at the par-4 10th. Ogilvy then birdied the par-5 12th to reach 10 under.
He kept on cruising with a birdie at the par-5 17th and landed his approach within 8 feet of the hole for a birdie at the closing hole.
'I didn't really do anything wrong, I guess,' said Ogilvy. 'I hit the ball really well.'
Wetterich, whose best career finish on the PGA Tour was a tie for eighth at this event in 2002, kept his bogey-free streak going with three consecutive pars from the first. He then jumped to 14 under with back-to-back birdies starting at the fourth but stumbled to his first dropped shot of the tournament at the par-5 sixth.
The 31-year-old played his second shot to 7 feet for a birdie at the ninth but he found trouble on the inward half with a bogey at the 10th.
'The day started off pretty good,' said Wetterich. 'Then I made the turn and it was a totally different ballgame.'
Wetterich then missed the green en route to a bogey at the par-3 11th and had a bad bounce in a hazard for a bogey at the par-3 15th.
Wetterich responded at the par-5 17th and ran his second shot from the rough into a green-side bunker. He got up and down for a birdie and parred his remaining hole for a round of 72.
'I thought I hung in there really well today,' Wetterich said. 'I made a few mistakes mentally, maybe a bad club here or a bad club there, but I think I held it together pretty good.'
Janzen birdied the second and the third to take the lead early on at 13 under but fell one shot back with a bogey at the eighth. He drained a 7-footer for a birdie at the 10th to get back to minus-13 but struggled to a bogey at the 13th. The late bogey at the 18th then left him one shot off the pace.
'I think I'm in a great position for tomorrow,' said Janzen, whose last victory came at the 1998 U.S. Open. 'I feel like if I can go out tomorrow and just play the best round of golf I've ever played, I'll win.'
Fred Couples shot a 6-under 66 to move into a tie for sixth with Robert Damron at 8-under-par 208.
Match Play winner David Toms was one shot further back at 7-under-par 209 along with PGA Tour rookies Kevin Stadler and Sean O'Hair.
World No. 2 Vijay Singh finished six shots off the lead in a group at 6-under-par 210.