Augusta, GA ( - Bill Haas has never contended in a major before, but he hopes to change that this week. Haas opened the 78th Masters with a 4-under 68 on Thursday and that gave him a 1-stroke lead.

Haas, a five-time PGA Tour winner, does not own a top-10 finish in a major and he had never broken 70 at Augusta National Golf Club before this round. He changed that in round one as he mixed six birdies with two bogeys for his 68.

Defending champion Adam Scott dumped his tee shot in the water on the 12th and walked off with a double-bogey. Scott recovered to shoot 3-under 69, which left him tied for second place with Bubba Watson and Louis Oosthuizen, who battled in the 2012 playoff that Watson won.

Kevin Stadler, who played a few groups ahead of his father, Craig, carded a 2- under 70. The younger Stadler was joined in fifth place by K.J. Choi, Jimmy Walker, Brandt Snedeker, Jonas Blixt, Marc Leishman and Gary Woodland.

The Stadlers were the first father-son duo to compete at the same Masters tournament.

Fred Couples, Rory McIlroy and Jordan Spieth were among eight players tied for 12th at minus-1.

Three-time champion Phil Mickelson stumbled to a 4-over 76, which left him tied for 67th. His round included a triple-bogey on the seventh and a double- bogey on the 15th. Mickelson also carded two birdies and one bogey.

Haas, whose best finish in a major is a tie for 12th at the 2011 PGA Championship, stumbled out of the gate with a bogey on the first. He bounced back with a birdie on No. 2 and reached red numbers with a gain at the fourth. After a pair of pars, Haas converted another birdie effort on the seventh.

The reigning AT&T National champion ran off five consecutive pars from the eighth to remain near the lead.

Haas, who has won in each of the last four seasons on the PGA Tour, grabbed the lead at 3-under when he birdied the 13th and made it two in a row with another birdie on the 14th. He coughed up a shot on the 17th, but closed with a 5-foot birdie putt at the last to get in at 4-under.

The 68 tied Haas' low round in a major.

"I made some nice putts. A couple 20-footers to go in that sometimes you're happy to 2-putt, so to have those go in can swing your score one way or the other," said Haas, who won the FedExCup in 2011.

Scott opened with a birdie on the first. After four pars, Scott birdied the sixth and picked up another at the par-5 eighth.

The Australian gained the lead at minus-4 with a birdie on the 10th. Scott's tee shot at the par-3 12th found water and that led to a double-bogey.

"I just received the most incredible ovation as I came to the 12th tee, and maybe got caught up in it a bit, and hit the worst shot of the day. I only hit one bad shot I felt like, and that was it, in the water. Actually, my first ever trip into Rae's Creek on the 12th," Scott said of his tee shot on No. 12.

Scott got one stroke back with a birdie on the 14th. He closed with four straight pars to end one behind Haas.

"The Masters is usually the most nervous I am all year and it takes a few holes to settle down, at least, but today I was very comfortable and enjoyed every minute of it. It was a beautiful day to play golf," Scott stated.

Watson opened with a pair of pars before sinking a birdie effort on the par-3 third. He ran off nine consecutive pars from the third to remain in red figures.

The 2012 champion birdied the par-5s on the back nine, Nos. 13 and 15, to move to minus-3. He closed with three pars in a row to wrap up the only bogey-free round of the day.

"When it gets breezy around here, it comes in all directions, every hole switches. My whole goal this week is hitting greens. I missed one green by six inches and one green by three feet," Watson said. "That's my goal. Hit greens and let the score be what it's going to be. I played very solid and didn't make any mistakes."

Oosthuizen stumbled to a bogey on the first, but came back with birdies on two and three. After four pars in a row, the 2010 British Open champion dropped in back-to-back birdie tries at eight and nine to make the turn at minus-3.

The 2012 Masters runner-up faltered to a bogey at the 12th, but atoned for that mistake with a birdie on the 15th. Oosthuizen traded a bogey on the 17th for a birdie at the last to share second place.

"The wind was really swirling out there. Probably got me thinking a bit much on 12, then I hit behind the ball and didn't get it over the water," said Oosthuizen. "I played nicely though."

NOTES: Haas tied for 20th last year at Augusta and that stands as his best finish in four Masters appearances. He has had six previous first-round leads on the PGA Tour and won one of them ... Scott is trying to join Jack Nicklaus, Nick Faldo and the injured Tiger Woods as the only back-to-back winners of the Masters ... Scott, Henrik Stenson (73) and Jason Day (75) could all take over the top spot in the world rankings with a win this week ... Sergio Garcia made his 59th consecutive start in a major ... Ryan Moore, the par 3 contest winner, struggled to a 5-over 77 and is tied for 75th.