Padraig Harrington admits that he has a mountain to climb if he is to claim the Order of Merit title for the first time at Valderrama today.

Victory in the Volvo Masters would guarantee him a career objective that he rates just below a major title in terms of its importance.

But lying four strokes adrift India’s Jeev Milkha Singh with a round to play, he knows that he needs one of the rounds of his life to deny rivals Paul Casey, David Howell and Robert Karlsson the Vardon Trophy.

“Obviously I've got a difficult day ahead of me,” said the Irishman, who is tied for 13th place on one over par after slipping to a disappointing 72 with three back nine bogeys. “Four behind is not the end of the world, but I've put a lot of people between me and the lead and you've got to think somebody is going to shoot a decent score.”

If Harrington finishes second he will win the Order of Merit, provided neither Howell nor Karlsson win the event. If he finishes third on his own, he needs Casey to finish outside the top 35 for neither Howell nor Karlsson to finish ahead of him. He cannot afford a tie for third.

That said, Harrington cannot afford to play for second, though he would obviously settle for the 30th runner-up finish of his career this time around.

“I can only play to win the tournament,” he said. “Four shots certainly isn't insurmountable. But when I was coasting along at two under par and having birdies and things, it was a lot easier prospect of winning this tournament than it is now.

“You need things to go right when you are trying to win a tournament and unfortunately for 36 of the 54 holes I haven't been making the most of my scores. I am hopeful that tomorrow I am building up all those putts for 18 holes of sublime golf.”

Like Karlsson, Howell must win today to top the money list and summed it all up nicely, adding: "It's going to be exciting and it's going to take a great round from one of us tomorrow to pull this thing off."