Red-hot Charles Howell III set the target for overnight leader Padraig Harrington in the Nissan Open at Riviera.

The Augusta star, 27, rattled in six birdies in an immaculate six under par 65 to grab the clubhouse lead on eight under par at Hogan's Alley.

That left him tied with Harrington at the top after the Dubliner's scintillating 63 in the opening round.

European No1 Harrington was one of the late starters and immediately found himself in the chasing bunch when he bogeyed his opening hole.

Left with a tricky 40 yard pitch over a bunker at the driveable, 315-yard 10th, the European No 1 had little green to work with and flew his approach over the back.

The ball nestled down in the heavy collar of rough behind the green and while he chipped back to four feet, his par putt failed to drop.

But he bounced back straight away with a birdie at the par five 11th, where he pitched stone dead from 20 yards

Howell hardly put a foot wrong all day and took advantage of perfect early conditions when he followed birdies at the 10th and 11th with four in a row from the 17th, his eighth.

American Pat Perez hit a two under par 69 to trail Howell by a shot on seven under and he was soon joined on that mark by Sergio Garcia.

The Spaniard chipped for a birdie at the par five 17th on his way to a solid 68 and prepared to watch how Harrington dealt with bumpier afternoon greens.

Garica said: "That was pretty solid. I guess it could have been a few shots lower but all I can do now is look and see how Padraig gets on."

David Howell, another of Harrington's Ryder Cup team mates, also made a move to join Garcia on seven under thanks to a fine 68.

Dubliner Paul McGinley struggled with the putter in his second round and was six shots adrift of Howell III and Harrington on two under par with two holes to play.

McGinley still had two holes of his first round to complete early in the day but had to settle for a one under par 70 after a bogey at his final hole.

But he bounced back straight away in the second round when he reached the par five first in two and two putted from 60 feet for his birdie.

A bogey at the sixth, where he failed to get up and down from greenside sand, dropped him back to one under par for the tournament.

But it was a frustrating day on the greens for the Dubliner after that as he failed to hole his share.

His luck appeared to change at the 479 yard 12th, where he came up 36 yards short with his approach but holed out from the rough for an unlikely birdie.

But he soon came back down to earth at the next, missing a five footer for birdie that would have put him in the top 20.

Stuck on two under par for the tournament, the Ryder Cup star finally holed a putt at the 15th but it was a 16 footer for par after he had found greenside sand with his 178 yard approach.