BILL HAAS claimed the early clubhouse lead in the 78th US Masters as the shortest hole at Augusta National had a major impact on two players trying to get into the record books.

Haas, whose father Jay was third here in 1995, carded an opening 68 to finish four under, a shot ahead of defending champion Adam Scott.

Masters rookies Kevin Stadler, Jonas Blixt and Jimmy Walker were among a six-strong group on two under.

Their fellow debutant, Scot Stephen Gallacher, was in outright second when he birdied the ninth to reach the turn in 33, but a hat-trick of bogeys from the 10th halted his charge.

The 39-year-old birdied the 15th and eventually signed for a 71, a highly creditable effort.

He said: "I only hit one poor drive, on 10, I was happy to get under par and stay in the red.

"I played with Sandy Lyle, Jose Olazabal and Miguel Angle Jimenez in practice. Their advice was great: you don't go for flags, you go for positions. It is a special course, it is Augusta."

Scott was four under par after a flawless opening 11 holes, with one of his birdies on the par-four 10th where he sealed victory on the second hole of a play-off with Angel Cabrera last year.

But the Australian - aiming to join Jack Nicklaus, Nick Faldo and Tiger Woods and win back-to-back titles - dumped his tee shot on the short 12th into Rae's Creek to run up a double-bogey five, before three-putting for par on the 13th and 15th.

"I was very happy with the way I played ­today tee to green," said Scott, whose 69 matched his lowest Masters opening round last year and in 2010. "It was really how you hope to come out and play at any major, and especially the Masters. I was really solid.

"I hit the one poor shot on 12, which obviously cost me a couple of shots, but very pleased to get off to a good start and there's no doubt winning the Masters last year had me a little more comfortable."

Three groups ahead of Scott, 50-year-old Miguel Angel Jimenez was four under after 10 holes in his bid to become the oldest winner of a major, but dropped a shot on the 11th and found water off the tee on the 155-yard 12th on his way to a 71.

Pre-tournament favourite Rory McIlroy safely found the 12th green but three-putted and did the same on the 18th to also card a 71.

Haas had not broken 70 in 16 rounds at Augusta but recovered from a bogey on the first with six birdies, including from five feet on the 18th after also dropping a shot on the 17th.

"I knew about that stat before the round so to shoot in the 60s feels great," Haas said. "There is a lot of golf left but I'm ecstatic with today."