US Tour/WGC Invitational:Rory Sabbatini set a target for the rest of the field to chase at the WGC Bridgestone Invitational with a blistering finish to his second round yesterday in Akron, Ohio.

The South African had shared the one-shot overnight lead with England's Paul Casey and American Hunter Mahan on three under par at the Firestone Country Club's testing par-70 South Course.

Padraig Harrington birdied two of the last four holes for a second-round 69 and a halfway total of 141 to keep Sabbatini in his sights. Out in level-par 35, Harrington birdied the 15th and 18th for 34 home.

Darren Clarke, meanwhile, dropped four shots in the last five holes for a second-round 76 and a six-over par total of 146. Paul McGinley is on the same mark after a 74.

But while Casey was one of the many to struggle in difficult early conditions, carding a three-over round of 73, Sabbatini recorded a second consecutive 67.

Mahan went out among the afternoon starters and was two over par for the round after 13 holes.

Sabbatini was one of the handful of players out on the course who was actually improving his score in humid, 85-degree heat with a breeze that started out light but caused problems in spells throughout the day.

The South African made the turn in 34, with birdies at the first and fifth holes before a bogey at the sixth.

Another dropped shot stalled Sabbatini at the 14th but he bounced straight back with birdies at 15, 16 and 17 before closing with par to leave him at six under for the tournament.

"It's a matter of picking and choosing your targets out there," Sabbatini said. "There are just opportunities that you have that you can be aggressive, but you have to kind of back down and just give the course respect, otherwise it'll hit you pretty quickly.

"I didn't quite hit the ball as well as I did yesterday. I hit a couple more drives in that hay they call rough out there but it was a little more of a grind today, a little more work.

"I think the positive thing I can take out of it is that I did battle out there and came out on top."

Sabbatini was two shots ahead of US Masters champion Zach Johnson, who shot the lowest round of the day with a five-under 65, later matched by Davis Love to take the former USPGA champion to one under.

Scott Verplank was in the clubhouse in third place on two under following a 68.

Boo Weekley had joined Johnson on four under with an eagle three at the par-five second before three bogeys and a double bogey at the ninth derailed his charge.

Casey, though, had a day-long battle to stay in touch and finished the day at level par for the tournament, six shots adrift of Sabbatini.

Three bogeys and three birdies on the front nine set the trend and a birdie at 11th was followed by a bogey five at the 13th before a birdie at the par-three 15th sent him back to three under.

Then it fell apart again for the Ryder Cup star as Casey bogeyed the 16th and double-bogeyed the 18th for a disappointing end to a tough day.

"I struggled a bit today and found the rough and when you find the rough around this golf course it's very penal and tough to recover from," Casey said.

"However, we carry on. I'm even par and not completely out of this thing yet."

Lee Westwood had an inauspicious start to his second round, bogeying his first two holes having teed off at the 10th hole.

Clarke's good friend had started the day one off the overnight lead, but he bogeyed his first two holes at 10 and 11. He steadied himself with a run of six pars before birdies at the 18th, first and third took him to within a shot of Sabbatini, only to card bogeys at the fourth and sixth to end the day with a 71 at one under for the tournament.