John Daly, the two-time major victor who in May won his first PGA Tour Champions title and is playing via a sponsor exemption, birdied the 18th for a second-round 69 to make the 1-under cut at 143.
Four players are at five-under including Lucas Glover and Argentina's Emiliano Grillo. The winds blew out of the north - unusual for this area - at up to 25 miles per hour, creating an added challenge with driving, approach shots, the short game and controlling the ball on the par-72 course that measures 7,166 yards.
"I hit a good putt on 18". Steele finished two shots clear of his countryman Tony Finau. The putt that Steele said was "huge", however, was the seven-foot, six-inch putt for bogey on No. 14.
Bud Cauley, winless in five tour seasons, shot 66 to join defending championBrendan Steele (72) at 12 under.
"I had a really good ball-striking day.
The course played as opposite as it could, but still able to have enough knowledge of the course, to know where to miss and know where to be aggressive and seemed like it worked out pretty good".
The 2017-18 PGA Tour season-opening event proved be quite fruitful for the 47-year-old as he finally delivered on the course when it mattered.
Mickelson, who finished eighth here previous year, is seeking a first win since the 2013 Open Championship. "So it was nice to get going right away here in Napa and keep the momentum going", he said.
Steele won last year's Safeway Open in Napa, shooting a 65 in the final round.
The current leader Tyler Duncan was tied at the top after the first round but bogeyed on the second, third and fourth to sit at one under for the day after four second-round holes on the front nine.
He added an eagle on the fifth but followed with a bogey on the next hole.
Hadley finished 12 strokes under par, tied with Phil Mickleson. He has not played a PGA Tour-sanctioned event since the 2015 Presidents Cup.
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Paddock's girlfriend, who was out of the country at the time of Sunday's shooting, said she had no idea he was planning an attack. Authorities still have no idea what caused retired accountant and chronic gambler Stephen Paddock to snap.