(CNN) -- Padraig Harrington has retained his lead at the halfway stage of the Bridgestone International after carding a second successive sub-par round for the first time in four months in Akron, Ohio.
Padraig Harrington needs a good finish to help his chances of reaching the Fedex Cup playoffs.
The Irishman, returning to form ahead of the defense of his PGA Championship title, leads by one shot at the World Golf Championships event following a one-under-par 69 in the second round on Friday.
Harrington, who will be paired with world No. 1 Tiger Woods and 2002 PGA winner Rich Beem in golf's fourth major of the season at Hazeltine next week, was on seven-under 133 as his overnight lead lead was trimmed by one stroke.
South African Tim Clark carded 68 to claim second place ahead of American Scott Verplank (69), whose compatriots Steve Stricker (69) and Jerry Kelly (65) were on four-under alongside Thailand's Prayad Marksaeng (70).
Woods, who cruised to his third Buick Open title last weekend and is a six-time winner at Firestone, was lurking in a group of nine players two strokes further back -- five shots off the lead -- after following up his opening 68 with a 70.
He was tied for 13th with British Open champion Stewart Cink (69), U.S. Open winner Lucas Glover (69), Masters champion Angel Cabrera (68), two-time major winner Retief Goosen (67) and 1997 PGA victor Davis Love (67).
Woods, who started on the back nine, birdied the 16th but then carded bogey-fives at 18 and three before picking up a birdie at his penultimate hole.
World No. 2 Phil Mickelson was a shot further back on one-under 139 after adding a 69 to his opening 70, while defending champion Vijay Singh dropped off the pace with a 73 which left him tied for 54th on 143 with fellow former top-ranked player Ernie Els (72).
Harrington is seeking to qualify for the end-of-season FedEx Cup play-offs, which start later this month with the Barclays tournament at Liberty National in New Jersey.
With the top 125 players in the FedEx Cup standings gaining entry, he needs to finish strongly at Firestone and Hazeltine to improve on his current 142nd place.
"It's going to be difficult, too, because with competing events, like I moved quite substantially back during the Open," he told reporters.
"I made the cut there, didn't have a great week, but I moved back a half a dozen spots, so it's not easy. The bigger the events, these two events, it's actually harder to move forward than in regular weeks."
Harrington, who has been struggling after redeveloping his swing, carded two birdies and a bogey-five on the eighth hole on the South Course.
"I was a bit cautious today. I was more worried about my misses rather than having that sort of confident attitude and going after a few more pins," he said.
"You know that if you shortside yourself you're going to have difficulty getting up and down. But you've got to make some birdies.
"My short game has been good enough, so I probably should be a little bit more aggressive over the weekend."