Akron, OH (My Sportsbook) - Padraig Harrington managed a one-under 69 on Friday, but it was enough to stay on top of the leaderboard after the second round of the WGC-Bridgestone Invitational.

Harrington, the overnight leader by two and a double-major winner in 2008, finished 36 holes on the South Course at Firestone Country Club at seven-under 133 and is one stroke clear of Tim Clark, who shot a two-under 68 on Friday.

Tiger Woods, a six-time titlist at this championship and last week's Buick Open winner, could do no better than an even-par 70 in the second round. He's in at two-under 138.

"You just have to be very patient. This golf course is playing like it normally does, and it's very similar to a major championship," said Woods, who narrowly missed a slew of putts on Friday. "A good number this week is going to be somewhere in the high 60s and more than likely you can move up the board."

Woods started on 10 and birdied the par-five 16th to get into red figures. He had a tough lie and hit a tree en route to a bogey at the 18th, then he dropped another shot at No. 3.

Woods birdied the par-four eighth and parred nine to get his share of 13th.

Phil Mickelson returned to the tour this week for the first time since a runner-up finish at the U.S. Open. He missed most of the summer to be with his wife and mother who are both battling breast cancer.

On Friday, Mickelson, a two-time winner this year, including the WGC-CA Championship, flew out of the gate with an eagle at two. He posted back-to- back bogeys at nine and 10, but responded with a birdie at the 11th to get back to one-under.

At the last, Mickelson drove into the trees and hit a crazy shot right of the green. He hit a spectacular chip to two feet and tapped in for a routine Mickelson par.

All totaled, Mickelson finished with a one-under 69 and moved into a tie for 22nd at minus-one.

"I fought for pars a lot of the day today," said Mickelson. "I didn't have a lot of great birdie opportunities."

Scott Verplank carded a one-under 69 and is alone in third at five-under 135.

Two-time winner this year Steve Stricker (69), Prayad Marksaeng (70) and Jerry Kelly (65) are knotted in fourth place at four-under 136.

They are all looking up at an Irishman who has undergone sever swing changes since the beginning of the year.

"I was wholeheartedly into my technique for a while, and the last couple of weeks I've been much more into trying to get a bit more balance in my game," said Harrington, a three-time major champion.

It worked with a 64 on Thursday.

But on Friday, Harrington played a much simpler round of golf.

He birdied the par-five second hole to reach seven-under par for the championship. Harrington then parred his next five holes before a bogey at the eighth knocked him down to minus-six.

Harrington had plenty of chances on the back nine. He missed a 10-footer for birdie on the 10th, but cashed in on a long birdie putt at No. 13. Harrington made his 30-footer for birdie to return to seven-under, then slammed on the brakes.

"I was a bit cautious at times, I suppose only to be expected when you're leading the tournament," acknowledged Harrington.

He parred his final five holes, missing a 10-footer for birdie at 16 and a 25- footer at the last. It was good enough for the 36-hole lead as Harrington tries to regain his form from a 2008 season that netted him the British Open and PGA Championship.

Harrington, who also won the 2007 Open Championship, has one top-10 in the 2009 season and that came at the Abu Dhabi Golf Championship in January. He has missed eight cuts worldwide this year and his best finish since the tie for fifth at Abu Dhabi was a joint 11th at the Arnold Palmer Invitational in late March.

So forgive Harrington if he remains "cautious," but he will try and make some more things happen.

"I'll wait and see what tomorrow brings me," said Harrington. "You know that if you short side yourself you're going to have difficulty getting up-and- down. But you've got to make some birdies. I'll be a little bit more aggressive than I was today."

Alvaro Quiros fired a 65 on Friday and moved from a tie for 52nd to a share of seventh. Quiros was joined by Woody Austin (68), Zach Johnson (70), Hunter Mahan (69), Mike Weir (66) and Robert Allenby (69) at three-under 137.

There is no 36-hole cut in this exclusive event, but the defending champion went down the leaderboard.

Vijay Singh struggled to a three-over 73 and fell into a tie for 54th at plus- three.