Casey leads the Order of Merit with just two events remaining but has chosen to rest rather than play in this week's Mallorca Classic.

In contrast, his nearest rival on the money list, Ireland's Padraig Harrington, has made the event at Pula Golf Club a last-minute addition to his schedule following his victory in the Alfred Dunhill Links Championship earlier this month.

That win, Harrington's 10th European Tour title, lifted the Dubliner to within £147,900 of Casey and victory in Mallorca - worth £195,000 - would see him move into pole position ahead of next week's Volvo Masters at Valderrama.

However Montgomerie, eight times a winner of the Order of Merit title, believes history is against Harrington overhauling Casey.

"The winner of the Order of Merit will be the leader right now," said the 43-year-old Scot.

"Out of my eight Order of Merits seven have happened when I've been leading going into Valderrama. There was only one where I was behind Sam Torrance and then I managed to pull it right out of the bag at the end.

"It is difficult to come from behind in golf and to try to push. The more you push the worse it is. I would put a lot of money on Paul Casey being ahead and staying there.

"It's very difficult for Harrington or (David) Howell to come back and to win at Valderrama. Paul Casey has great potential and great length.

"There's no golf course in the world getting shorter any more. The greatest asset in golf these days is length. It has become a power game and he has all the power necessary to compete. He just needs to control what goes on inside his head."

Long time leader Howell - only overtaken when Casey won the HSBC World Match Play at Wentworth in September - is less than £17,000 behind Harrington in third place but is also not competing in Mallorca.

Howell has been suffering from the recurrence of a shoulder injury and admitted recently he felt he was going to "fall at the final hurdle."

Sweden's Robert Karlsson, another member of the victorious Ryder Cup team at the K Club last month, is still in contention and plays in Mallorca, but is more than £300,000 behind Casey and will need two great performances to stand a realistic chance.

At the other end of the money list, this week is the last chance for players to secure a place in the top 115 and keep their card for next season.

Scotland's David Drysdale currently occupies 115th place, less than £2,000 ahead of Yorkshire's Ian Garbutt.

A total of five of Europe's victorious 2006 Ryder Cup team are in the field with Harrington and Karlsson joined by Sergio Garcia, Paul McGinley and defending champion Jose Maria Olazabal, who collected his 23rd European Tour title - and his first for almost four years - last year.

In the process Olazabal extended the Spanish dominance of the Mallorca Classic, won in the inaugural year of 2004 by Miguel Angel Jimenez and 12 months later by Garcia.