Dudley Hart leads the way with opening 64

Considered the PGA Tour's party stop with over a half-million rowdy golf fans expected to crowd onto TPC Scottsdale Stadium course for the $6 million event, Hart kicked off the festivities with a tidy round that included just one bogey.

Playing the back nine first, Hart started with three straight pars but then birdied seven of his next 10 holes to rocket up the leaderboard.

He added another birdie at the eighth, the only blemish a bogey six at the par five 15th.

Lurking one shot back is world number 18 David Toms, who mixed seven birdies with single bogey for a six-under 65, one shot better than fellow Americans Billy Mayfair and Bart Bryant on five-under 66.

Charles Howell III, the Fed Cup points leader with two runner-up finishes already this season, was again in excellent form returning a four-under 67 to sit three off the lead.

In contrast, twice Phoenix champion and world number five Phil Mickelson continued his early season woes struggling to a one-over 72.

After finishing outside the top 40 in his only two other starts this season, Mickelson produced another messy display littered with six bogeys, three birdies and an eagle as he prepares to defend his U.S. Masters title.

"It wasn't a very good round," Mickelson told reporters. "I made a number of bogeys and made some good birdies, but just didn't get it under par.

"I took three, four months off and I knew my game would be a little rusty, and it has been."

World number seven Vijay Singh also continued to fight to find his best form, firing an even par 71.