American duo lead Masters

His day was in marked contrast to that of compatriot and overnight leader Justin Rose, who shot a horrendous round of 81.

Casey's only mistake came at the tricky sixth - and he just failed to convert a birdie chance at the last for a 67.

The 26-year-old has picked up seven shots after his opening 75 and will be a major contender in the final round.

A delighted Casey said: "England are looking for another Masters champion and I would dearly love to fulfil that slot.

I have not let the course get me down and I am really looking forward to tomorrow Paul Casey

"I had a lot of fun out there. I think pairings count so much and Mark O'Meara was great to play with.

"I played some great golf. A couple of putts got away, but I was having a real ball. It's great to show the American crowds what I can do.

"I have not let the course get me down and I am really looking forward to tomorrow."

Rose's Masters hopes evaporated after he bogeyed the first three holes and dropped shots at six of the first nine holes.

The 23-year-old's day got worse as he bogeyed the par fives at 13 and 15 as well as dropping a shot at the 11th.

My good putts didn't go in, my good shots didn't get rewarded - every break seemed to go against me Justin Rose

The overnight leader did not make a single birdie and will start the last round nine shots off the lead, compared to the two-shot lead he had at the start of the day.

"Whether you believe me or not I felt in a great frame of mind going out there," said Rose, who had had just two bogeys in his first 36 holes.

"I hit the ball beautifully on the range. I just got off to a bad, bad start and every little minor mistake got punished.

"It was tough. My good putts didn't go in, my good shots didn't get rewarded. Every break seemed to go against me. Yesterday it would have gone my way.

"I got a beautiful ovation at the last. That was a nice touch.

"No matter what happened today it was going to be a great learning experience. At the age of 23, it's not the end of the world."

Compatriot Ian Poulter carded a 74 and will begin Sunday's final round on six over par.

After a dreadful start which saw him card three bogeys in the first five holes, he birdied the 10th, 13th and 15th, although there were dropped shots at the 11th and 16th.