Between the "big three" of men's golf, Jason Day, Jordan Spieth and Rory McIlroy have won three Majors and 17 tournaments since the start of 2015.

However, it is the unlikely figure of Adam Scott who Michael Campbell has tipped to win at Oakmont Country Club this year.

Campbell, who won the 2005 US Open, believes that the Australian, who has two titles this year - the Honda Classic in February and the WGC-Cadillac Championship in March - has displayed consistency and accuracy in his irons, and currently sits at the top of the PGA Tour approach-the-green rankings.

"In shots gained, he's leading so far so he's got a huge advantage," said Campbell, who is now a Fox Sports pundit. "I just watched Scott play a few holes and he is very much focused on playing well this week. He's leading fairway to green - that's my theory behind choosing him. His striking this year has been phenomenal."

However, the likelihood of a win by one of the "big three" remains considerable as confidence is high among them, observed the 47-year-old Kiwi.

"The big three have momentum and confidence so they have the edge over Scott in terms of mental capacity," he said.

Day and Spieth won The Players Championship and the Colonial tournament respectively last month, while McIlroy clinched the Irish Open, which was hosted by his foundation.

No matter how high their confidence is currently, whoever emerges victorious this weekend will have to contend with the brutal course conditions.

"The wet weather makes the green softer for the first couple of rounds and the rough even thicker and heavier when you make contact with the ball," said Campbell.

"The guy who handles his mental capacity and damage control the best will win. It's about controlling the golf ball in the right direction as well as your mind. Mental toughness is the true test of golf this week."

Despite the quality of golfers on show, this week's US Open will still miss Tiger Woods, who has not played competitively since last August at the Wyndham Championship. "When Tiger plays, he is a different animal. He's transcended the game over the years and we still need him," said Campbell, who added that the current big three have done well to represent the sport in his absence.

"The big three are carrying the flag nicely... Rory and Jason are always sharing their stories throughout their life on tour. But when Tiger plays a tournament anywhere in the world, it's different."