Of all the great records he has chalked up in his career, there is one label that Phil Mickelson really wishes he did not own: most second-place finishes at the U.S. Open.

By any standards, Mickelson's five runner-up finishes at the U.S. Open are a great achievement and a source of pride to the American because the tournament is traditionally the toughest major to win and does not suit his swashbuckling game.

However, it also remains a source of deep frustration for the popular American because he has never won his national open and believes he should have by now.

"If you look at my game from 20,000 feet, you'd say, 'Well, that's probably not the best setup for the way he likes to play,'" said Mickelson, who was the U.S. Open runner-up in 1999, 2002, 2004, 2006 and 2009.

"And yet five times I've had opportunities, I've come close. Could have, should have won a few of those. So it gives me the belief that I can compete and be in contention on Sunday in this tournament."

Mickelson's form heading into the July 14-17 U.S. Open at the Olympic Club in San Francisco has been patchy. He outscored Tiger Woods by 11 shots in the final round to win the Pebble Beach National Pro-Am in February then made a three-way playoff at the Northern Trust Open, won by Bill Haas.

The 41-year-old Californian finished tied for third at the Masters and has had five top-10 finishes from the 13 events he has contested.

But at his final outing before the U.S. Open, Mickelson withdrew from the Memorial in Dublin, Ohio, citing fatigue, raising doubts about his mental state heading into the year's second major.

"I don't know why it's been like that, but it's something I need to fix, as far as being ready to play on Thursday, Friday," he said. "I don't see myself as a favorite, but I think I've developed a good game plan as to how I want to play the golf course.

"I feel that I should be able to play to that game plan and post a number that I feel will be competitive."

Despite admitting to feeling lethargic, Mickelson said the tournament organizers did him a favor by putting him in the same group as Woods and Bubba Watson for the first two rounds.

"It's fabulous," Mickelson said. "First of all, I get excited to play with Tiger, I love it. I think we all do. He gets the best out of me. I think when it's time to tee off on Thursday I'll be ready to play.

"One of the issues I've had this year (is) I've been a little mentally lethargic on Thursday and Friday. I won't be this week."

(Editing by Frank Pingue)