DUBLIN - Phil Mickelson's shirt already was stained with patches of sweat, the sign of someone hard at work. This was more a case of oppressive heat and humidity at Muirfield Village, because the Masters champion had yet to play his pro-am Wednesday.

Truth is, the hard work is just beginning.

“It starts my stretch now through the U.S. Open, and what a great place to start,” Mickelson said.

He returned to the Memorial for the first time since 2002, having played only twice since his two-shot victory at Augusta National, neither event particularly memorable. Mickelson showed plenty of rust in New Orleans when he tied for 15th, and loads of fatigue a week later at the Wachovia Championship, where he was never near the lead.

But after three weeks off, Lefty has his eyes on Winged Foot three weeks away.

“I thought that New Orleans was a very emotional week, seeing the city and being there. And it took a little more out of me, and I was just tired,” Mickelson said. “Now I'm excited to get back out and play. I have the energy and the motivation to go work hard and practice. It was tough there for a week or two. And now after a nice, little relaxing break, I'm ready to get back at it.”

Mickelson spent much of the holiday weekend at Winged Foot before coming to Muirfield Village, where so much has changed since the last time he was at the Memorial.

It's the first time Mickelson has as many majors as any other player in the field.

For one thing, he didn't have any majors in 2002, and now has won three of the last eight. Of more significance, this is the first time tournament host Jack Nicklaus (18 majors) is not playing, and the first time Tiger Woods (10 majors) has skipped the Memorial since he turned pro. Woods hasn't played since his father, Earl, died May 3.

The other big change is the bunkers, which are getting far more attention than the weather.

Nicklaus suggested - and the PGA Tour concurred - that he would use specially designed rakes that create furrows in the sand, turning bunkers into true hazards. It will be harder to get spin on the ball, meaning players will have a tougher time saving par from around the green, or getting near the green when they're in a fairway bunker.

“It's certainly the easiest way to make the golf course harder, to change the rakes,” David Howell said. “It's the cheapest way.”