AUGUSTA, Georgia - As the first of the year's four majors, the Masters has always been keenly anticipated and this week's edition should be one of the most open in decades with the absence of world number one Tiger Woods.

Former world number one Rory McIlroy has predicted that 70 players in the field of 97 are capable of clinching the coveted green jacket with multiple champion Woods out after having surgery to repair a pinched nerve in his back.

Three-times champion Phil Mickelson feels that figure will depend on course conditions.

"The greens are getting back to what I call Masters speed," Mickelson told reporters at a sun-splashed Augusta National while preparing for Thursday's opening round.

"If that's the case, if the course plays firm and fast, I think you're looking at less than a dozen (players). But if it doesn't, I think you're looking at almost half the field."

Mickelson, a perennial contender at Augusta National, faced injury concerns of his own after withdrawing from last month's Texas Open with a pulled abdominal muscle, but he has fully recovered after doing extensive physiotherapy work.

"Physically, I feel great," said the 43-year-old American, who will be seeking a sixth major title. "This is my favourite week, and the course is in spectacular condition, as always.

"I just love everything about this tournament. This course has always been a course that I felt comfortable on and I've played some of my best golf here."

Whether or not Mickelson is a significant factor over the next four days, the possibilities are seemingly endless when it comes to likely winners of the 78th Masters.

Extraordinary depth

The last seven editions have produced seven different champions and golf's extraordinary depth of talent has been showcased on the 2013-14 PGA Tour where there have been 18 different winners from the 21 tournaments so far completed.

Though Masters debutants have generally struggled on the heavily contoured greens at Augusta National, with only three first-timers clinching the title since the tournament was launched in 1934, McIlroy believes that is no longer the case.

"There's so many guys here this week who will feel like they have a chance to win," said the 24-year-old Northern Irishman, a double major champion. "I would say 70.

"You've got guys who are coming here for the first time, like Patrick Reed or Jordan Spieth who I'm playing with in the first two rounds, and they are going to stand on the first tee and think, 'I've got a great shot at winning this tournament.'"

Reed has triumphed three times on the PGA Tour since last August while fellow American Spieth was named the U.S. circuit's 2013 rookie of the year after a remarkable debut season that included a maiden victory at the John Deere Classic.

The list of potential champions is a long one, as demonstrated by the 'unlikely' Masters victories of Canada's Mike Weir in 2003, American Zach Johnson in 2007 and South African Trevor Immelman in 2008.

Back-to-back Masters wins have been rare with only three players accomplishing the feat. Jack Nicklaus was the first in 1966, and he was followed by Nick Faldo in 1990 and Woods in 2002.

Defending champion Adam Scott of Australia will have a good opportunity to add his name to that illustrious company, having climbed to number two in the world rankings with a superb run of form late last year.

He clinched his 10th PGA Tour title at The Barclays in August before ending his season by winning the Australian PGA and Australian Masters, partnering Jason Day to land the World Cup team event and finishing second at the Australian Open.

Title favorites

Though Scott has not triumphed since, he has recorded three top-10s in his last five PGA Tour starts and will tee off among the title favourites.

"I've performed extremely consistently (at the majors) in the last couple of years," said the 33-year-old Australian. "Realistically I've given myself two or three chances to win and won one of them.

"I'm happy with that because the trend is going in the right direction and I've just got to keep that going, strike while the iron is hot and keep creating these chances.

"I'm playing really well. I really like the last couple week's work I've done," added Scott, who became the first Australian to win the Masters by edging out Argentina's Angel Cabrera in a thrilling playoff.

McIlroy will be eager to atone for his nightmarish final-round meltdown three years ago when he squandered a four-shot overnight lead with a closing 80.

The Northern Irishman will also be champing at the bit to prove that his struggles on and off the course for much of his 2013 campaign are now behind him, and his form so far this year has been encouraging.

"I have no ill feelings towards 2011," said McIlroy. "I thought it was a very important day in my career. It was a big learning curve for me.

"My preparations have been good. I'm excited to be back here. It's probably the most anticipated week of the year."