A hole in one from Dustin Johnson helped him regain the lead in the second round of the Northern Trust Open.

The ace helped the overnight leader regain the initiative from Steve Stricker at a rainy Riviera Country Club.

Big-hitting Johnson had shot an opening seven-under-par 64 on Thursday to lead by a stroke from Argentina's Andres Romero and fellow American Kevin Stadler.

Day 2 Leaderboard

But as he waited to get his second round under way at Pacific Palisades near Los Angeles, world number three Stricker had moved to the top of the leaderboard.

Stricker fired a seven-birdie, one-bogey 65 to take the clubhouse lead at 10 under, with Stadler shooting a level-par 71 to finish at six under alongside Tim Wilkinson, who had carded a 67.

Johnson, though, soon made inroads with birdies at the par-five first and the par-three fourth and moved into the outright lead when he aced the 199-yard, par-three sixth.

Romero was trying to keep pace with Johnson and he had got to eight under after two birdies in his first seven holes, while England's Justin Rose was going well, four under for the day and six under for the tournament after 11 holes.

A further shot back was compatriot and Ryder Cup team-mate Luke Donald, also starting from the 10th tee and two under for his round after seven holes. That got him to five under alongside Americans Anthony Kim (66), Steve Marino (67) and Ricky Barnes (71), with JB Holmes and Japan's Ryo Ishikawa on the same mark after their front nines.

Defending champion Phil Mickelson enjoyed a much a better day in the rain than he had on Thursday when he had shot a one-over 72. The world number two got his bid for a third Northern Trust Open title in a row back on track with a 66 to leap to four under alongside fellow American Brandt Snedeker (72) and South Africa's Ernie Els (70).

Mickelson credited a late-night chat with both his swing coach Butch Harmon and putting coach Dave Stockton for turning his fortunes around.

"I felt like I wasn't far off after yesterday's round, even though the score didn't reflect it," Mickelson said. "I had a good conversation with Butch and Dave Stockton last night, and I think it settled in today.

"I was able to make the last adjustment and it felt great. I hit the ball much better and putted much better."

Mickelson had taken 32 putts in his opening round, but needed just 26 in the second.

"I'd been a fraction off on the greens and catching lips but it was a good talk with Stockton and that last bit of fine tuning, a little adjustment, and it all seemed to click today.

"Even though conditions were much more difficult I played a lot better."

With the halfway cut mark hovering around the one-over-par mark but conditions and scores worsening as the afternoon wore on, some of the later starters were having to be mindful of making the weekend's play.

Ireland's Padraig Harrington was one of those as he bid to shake off some rust in his first tournament of the year. The three-time major winner had opened with a 72 and started his second round well with two birdies in his first three holes but he was soon back at one over following bogeys at the fourth and ninth.

Martin Laird of Scotland was faring worse, three over after eight holes playing the back nine first, two over for the day.