American Duffy Waldorf fired a second successive six-under-par 66 to take a one-shot lead after the Tucson Classic second round in Arizona on Friday.
The four-times PGA Tour winner mixed eight birdies with two bogeys to finish on 12-under 132 at the Tucson National Golf Resort and Spa.
Overnight leader Mark Wilson, chasing his first tour victory, got to 13 under with nine holes to play but doubled-bogeyed the par-three 12th and also dropped at the par-four 14th on his way to a 69 and second place.
Big-hitting Bubba Watson returned a 67 to end up a further stroke back in a tie for third with fellow Americans Jerry Kelly (68), Bob Tway (66), Jason Gore (66) and Scott Gutschewski (67).
Germany's Alex Cejka (68) produced four birdies in a blemish-free display to secure a share of eighth place at nine under.
Britain's Justin Rose, playing his fifth U.S. event of the season, carded a 68 to share 36th place at six under, level with South Africa's Trevor Immelman who returned a 70.
The halfway cut fell at four-under 140.
Among those missing out were former world number one Nick Price and 2002 U.S. PGA champion Rich Beem (both on 141) and French Ryder Cup player Thomas Levet (144).
Zimbabwean Price, making his first PGA Tour appearance of the year, carded a second-round 69.
With the game's leading 64 players competing in this week's WGC-Accenture Match Play Championship at La Costa Resort and Spa in Carlsbad, California, the Tucson event offers some of the game's lesser lights a chance to shine.