Clarke - in contention after a 67.

Darren Clarke conceded he cannot catch the Open leaders at St Andrews but he remains confident he can challenge for the top 10.

Despite carding a 67 to reach six under that was still five behind leader Tiger Woods before he had even started his third round.

The Ulsterman knows his form is not the best on the greens - it cost him in rounds of 73 and 70 on the first two days - and although he had slightly more success today making a challenge for the top is beyond him.

"I'm too far behind. I have got to go and try to play well and try not to make as many mistakes and get myself into the top 10," said the Ryder Cup star.

"The whole tournament depends on what Tiger does. If he gets going again it is going to be very tough to catch him.

"If he does get too aggressive he might make a mistake or two which might let the other guys in but the way he is playing that is tough to see. He is playing smart and not making mistakes.

"You're always trying to catch Tiger. You never know what is going to happen, especially around here, but the way he is playing you know you are going to have to play very well to catch him.

"I'm playing okay but at the moment it is just not quite happening for me."

The 36-year-old got the start he wanted with a birdie at the first and despite dropping a shot at the next he had a remarkable run of four birdies in successive holes from the fifth.

He even managed to escape trouble at the 352-yard ninth after driving into gorse by the green, taking a penalty drop and chipping to four feet to turn in 32.

However, a freak drive at the 10th caused him problems, his five wood careering 290 yards into the wind and just reaching the fairway bunker. He had no room for a shot to the green so had to play out backwards and that cost him a stroke.

He dropped another shot at the 11 from one-and-a-half feet but a six-foot birdie putt at the next and another at the 13th moved him back to five under and a three-footer on 16 lifted him to six under.

Clarke missed the chance of a birdie at the last having driven pin-high to the left of the green, leaving himself a 141-foot eagle putt which he knocked to five feet but missed.

The Northern Irishman was superb on the greens last week at Loch Lomond but having struggled on Thursday he changed putters, although he did not think it had helped him that much.

"I've wasted a few [putts] but saying that I have holed a few. But it is another day of making too many mistakes," he added.

"I played well again. I hit a lot of really good shots, hit it very close around the turn and made a lot of birdies and then made a couple of mistakes, although 10 wasn't really a mistake.

"You can't really explain the tee shot on 10. I don't know what it's hit or how it has managed to go that far but I wish I could do it every time. I can't hit a five wood 290 yards into the wind, I just can't do it.

"Today I gave myself lots of chances and unfortunately I've not shot the score I could have done.

"But 67 is certainly about the worst score I could have shot."