The hard work has been done over the winter, and now Phil Mickelson faces the test of truth of what he believes is a rehabilitation of his wayward swing in his defence of the Masters that begins on Thursday.

A final-hole collapse at Winged Foot last June when he needed a par to win the US Open and took 6 followed by a dismal Ryder Cup showing in Ireland where a half-point was all he had to show for five matches convinced the 36-year-old Californian left-hander that an overhaul was required.

In particular, his driving that had been so vital a part of his Masters win last year had become errant and he was so concerned about that aspect of his game that he took a four-month break to straighten it out.

"I'm now able to drive the ball better than I ever have, and because of that I have a lot more confidence than in years past," he declared in a pre-Masters conference call. "Hopefully that will help me in the Masters because driving when I won in 2004 and 2006 was a critical element."

Driving accuracy has been a controversial topic this year with the R&A and USGA, the two principal governing bodies in golf, having declared their intent to limit groove volume in iron clubs because of the control it allows out of rough.

At Augusta, such precision is required into those enigmatic greens that the rough there, a recent innovation to a course where the originator, the legendary Bobby Jones, had envisaged no such thing, is already a telling factor.

"It puts a premium on accuracy because the first cut makes it much more difficult to get the distance control into the greens," noted Mickelson, who reckons driving accuracy at Augusta is under-rated. "We know how important it is to hit the ball the right yardage on those greens, so it does have an effect.

"But I think the biggest difference in Augusta is the length. The length in the last few years has made the course extremely long. I don't even carry a sand wedge he uses his lob wedge out of bunkers because there are no sand wedge shots for me.

"There are no par-4s I can hit a sand wedge into and on the par-5s I'm usually close enough to hit a lob wedge if I have to lay up."

The increased length, he reckoned, had brought the same clubs back into play as when he first played Augusta 16 years ago.

"I remember I hit driver, seven iron into the 18th in 1991. In the late 90s, early 2000s it became driver-wedge or driver-sand wedge. Now it's back to driver, seven iron. In fact, last year when it was wet I hit four and five irons."

Playing conditions this year are expected to be firm and fast, and although Mickelson's run-up to the Masters has been less than inspiring, that counts for little when this is the one that really matters and all the work has been geared towards this course and this competition since the last major championship, the US PGA at Medinah, where Tiger Woods won his second in a row after the Open at Hoylake.

Mickelson, like most of the principal contenders, has taken this week off to make his final preparations and reportedly had a seven-under-par 65 in practice at Augusta that could have been three better as he missed from inside 15 feet at each of the last three holes.

That augurs well for the prospect of the showdown everyone wants to see: a Mickelson-Tiger Woods head-to-head in the final round.

They have dominated the first major championship of the season for the last six years, having won five between them Mike Weir is the only infiltrator, in a similar way to Arnold Palmer and Jack Nicklaus winning five in a row between them from 1962.

Palmer, still undecided over whether or not to take on the role of honorary starter on Thursday, has said: "It helps the game to have that kind of rivalry. The more we can talk about Phil and his golf and the challenge to Tiger the better. They have different approaches and the competition is what it's all about."

With fairways expected to be running next week, that could bring more of the shorter hitters into the frame, such as South African Tim Clark, who was runner-up to Mickelson last year, and, of course, Weir.

"There are a lot of good players that I think can win the tournament even if they're not the longest hitters," said Mickelson, "but I do think distance is a big advantage there. The odds would kind of say longer hitters would win."