The U.S. Open is the only major championship in the Hall of Fame golfer's career keeping him from completing a career Grand Slam.

"These three provide me a great opportunity to finish out this final leg,'' Mickelson said Monday at Shinnecock Hills Golf Club, where the U.S. Open begins Thursday. "Certainly the way I've been playing this year and at the consistency level, as well as at a much higher level than I've played the last few years, gives me a great opportunity.

"But the last thing I'm thinking about right now is trying to win. I'm trying to get myself in position for the weekend because when you try to go out and win a U.S. Open, you will lose it quick.''

Mickelson is quite familiar with U.S. Open struggles. He finished runner-up at the tournament a record six times, including 2004 when along with winner Retief Goosen they were the only players to finish under par at Shinnecock.

Next year, the U.S. Open returns to Pebble Beach, where Mickelson has won the PGA Tour event four times; and where he tied for fourth at the 2010 U.S. Open (he was tied for 16th there in 2000). And then in 2020, around the time Mickelson turns 50, the U.S. Open will be at Winged Foot, where Mickelson famously double-bogeyed the 72nd hole in 2006 to lose by one to Geoff Ogilvy.

A victory this week at Shinnecock would make Mickelson the oldest U.S. Open champion and the second-oldest major champion, surpassed only by Julius Boros, who was also 48 when he won the 1968 PGA Championship.

"I've come close a few times in this tournament,'' he said. "I love the challenge. I really love the challenge, and I love that I have another opportunity to try and complete the career Grand Slam.''

Mickelson is grouped for the first two rounds with the other two active players who are one major away from completing the career Grand Slam, Rory McIlroy (Masters) and Jordan Spieth (PGA Championship).

He tied for 12th on Sunday at the FedEx St. Jude Classic and is ranked 20th in the world.