The American, dubbed one of the best players never to win a major, has finished runner-up at the U.S. Open twice in the previous four years but hopes to go one better at Olympia Fields when the 103rd Open gets underway on Thursday.

"I have tried to be patient in the Opens, not to try anything extravagant, knowing that the players are not going to run it high," he told reporters.

"That has been a strategy that has got me in contention.

"But I think this week I may have to take a few more chances, to get below par heading into Sunday -- because I think the leaders on Saturday night will be a few under par."

Mickelson has enough experience to learn from, having been the 'nearly man' so often.

Aside from his U.S. Open heartbreak, he has finished in the top three at a major on another five occasions, and also second to Tiger Woods on the PGA Tour money list for the last three years.

At last year's U.S. Open at Bethpage, New York, he trailed leader and eventual champion Woods by five shots going into the final day, and despite a last-ditch run, finished in the world number one's wake.

"I started the day too far back and something I need to improve on this year is not leaving myself five shots adrift," said the Californian, who celebrates his 33rd birthday on Monday.

Yet while Mickelson is willing to let his natural, aggressive tendencies shine through, he knows he cannot take risks off the tee at Olympia Fields, where the fairways are narrow and the rough never too far away.

He said: "My driving statistics have never been great, but the weeks of the U.S. Open they've been good ... you see me hit a lot of big cuts to get the ball in play.

"I try to hit the fairway, and with that I'm taking 20 yards off the potential tee shot. That will be the case this week, too."

After all that, if Mickelson is to claim a major victory come Sunday, he will have to deal with the mental pressure that has built over his 11-year professional career.

Although he insists he doesn't "really worry about it", such indifference is betrayed by his response to another line of inquiry.

"The way I deal with the expectations of me winning are to try to avoid it," he said.

"I try to avoid the surroundings here. I try to get my practice rounds in before people get here ... I find staying out of the environment is the best way to deal with it."