Lee Westwood, Phil Mickelson, Luke Donald, Graeme McDowell and Tiger Woods have extra incentive to win the U.S. Masters at Augusta this week.

London – Lee Westwood, Phil Mickelson, Luke Donald, Graeme McDowell and Tiger Woods have extra incentive to win the U.S. Masters this week.

Such is the logjam at the top of the world rankings, all five have the opportunity to leapfrog number one Martin Kaymer if the German fails to land the coveted Green Jacket at Augusta National.

“There are six players who could be the number one next week, that's how flexible things have become,” said Tony Greer, who helps compile the rankings.

“It all depends on what Kaymer does, of course, but there are so many combinations. The only player in the top seven who can't overtake Kaymer is (number six) Paul Casey,” Greer told Reuters on Monday.

“He can't quite do it because the points are divided by the number of events played and (number seven) Woods has got a very low events played criteria whereas Casey's is higher.”

Mickelson rose to third in the rankings after his Houston Open win on Sunday, behind Kaymer and Westwood and just ahead of fourth-ranked Donald and number five McDowell.

It is the first time in 14 years Mickelson has gone ahead of arch rival Woods in the rankings.

Woods, without a victory since the 2009 Australian Masters, has also plunged to his lowest position since he romped to a 12-shot victory at the 1997 Masters.

According to British bookmakers William Hill, Mickelson has now replaced his fellow American as the punters' favourite.

The odds on the left-hander retaining his Masters title this weekend have been cut from 9-1 to 13-2 following his victory in Houston while Woods has drifted to 10-1.

“We are seeing four bets on Mickelson to every one bet placed on Tiger. His days as the punters' pal are definitely over ... for now,” said Hill's spokesman Rupert Adams.

With the top 55 players due to compete at the first major of the season, Greer said this year's Masters field was the strongest since the world rankings were launched 25 years ago.

“The qualification criteria probably wasn't as good in 1986 as it is now,” said Greer.

“In the last 25 years something like 16 Masters have been won by someone in the top five of the rankings. It's a tournament the leading players win.

“Zach Johnson in 2007 and Angel Cabrera in 2009 are the only players outside the top 50 who have won the Masters since 1986.”

Greer also said the European representation at Augusta this week underlined how the balance of power in world golf had shifted in the past 25 years.

“When we started the rankings in 1986 only three Europeans made it to Augusta,” he explained. “This year there are 26 Europeans playing.

“There were eight Europeans in the top 50 of the rankings when we started and now there are 18 - exactly the same as the U.S.” – Reuters