Karlsson's first European Tour victory came at the Turespana Masters in 1995

Robert Karlsson will attempt to emulate Tiger Woods by claiming three titles in succession when the Portugal Masters begins in Vilamoura on Thursday.

Woods, who has also won four in a row, recorded the last hat-trick in 2006.

Karlsson has moved ahead of Padraig Harrington in the Order of Merit after wins in Cologne and then at St Andrews.

Another victory would leave Harrington needing to win the season-ending Volvo Masters, but Lee Westwood, who plays this week, also has an outside chance.

Westwood is a distant �275,00 off the pace but there is a top prize of �400,000 up for grabs at the Oceanico Victoria club this week and the 35-year-old, who won the Order of Merit in 2000, will also be competing at the final event, the Volvo Masters, in two weeks' time.

He has elected not to play in next week's Castellon Masters in Spain but Westwood reflected favourably on a campaign in which he finished a shot adrift of the US Open play-off between Woods and Rocco Mediate.

"I think it's been a great year," he said. "It's the first time I could have won a major, but I feel like sooner or later I ought to win. It's a fine line between winning and finishing second and third. Padraig has got a couple of years on me, and I'm building up experience all the time."

On his decision not to cram in the events in a bid for the Order of Merit he said: "I figured if I played three weeks in a row I would get run down. I've got a little cold - kids pass them on when they come back from school.

"I'm more likely to play well in the Volvo Masters, having another week off before."

Harrington, meanwhile, is now �112,000 behind Karlsson but is unable to reduce the gap this week, as he is in Bermuda competing in the PGA Grand Slam.

"I'll have a battle on my hands for the Order of Merit for sure. It's in Robert's hands now," Harrington admitted.

Another title the Irishman will be able to bring back with him, however, is the PGA Golfer of the Year, following his triumph in the USPGA Championship, and Karlsson said: "I still rate Padraig's year higher than mine.

"If you've won two majors there's no doubt who is the best player this year."

It will be the first time that 39-year-old Karlsson, who finished runner-up to England's Steve Webster in this event last year, has begun a tournament as a member of the world top-10.

Karlsson and Westwood have been paired alongside each other and also Spaniard Miguel Angel Jimenez, who is fourth on the current money list, for the opening two rounds.

Graeme McDowell and Ross Fisher also have outside hopes of securing the number one spot.