Technically, five players can still win the PGA European Tour order of merit title which concludes with this week's season-ending Volvo Masters in Valderrama; although the odds are stacked very much in favour of the one man from that quintet who won't actually be competing in the tour finale.

Ernie Els, who has decided to play in the clashing Singapore Open on the Asian Tour rather than include the Spanish gig on his schedule, is in pole position to claim the Harry Vardon trophy - a distinction he previously held in 2003 and 2004 - with those playing catch-up faced with very clear objectives if they are to overhaul him.

Quite simply, Padraig Harrington needs a top-three finish to overtake the South African, while also finishing ahead of England's Justin Rose, if he is to successfully defend his money title.

Rose, too, needs a top-three finish, while needing to be ahead of Harrington.

For the two Swedes, the picture is even clearer. Henrik Stenson would need to win, with Harrington and Rose finishing outside the top-two. Niclas Fasth is in an identical position, requiring to win and for Harrington and Rose to be outside the top-two.

As things stand, Els has a lead of 217,295 over Harrington; a margin of 217,952 over Rose; an advantage of 510,046 over Stenson, and a gap of 622,999 over Fasth.

Of those in contention for the money title, only Els (twice) and Harrington, last year, have previously won.

Harrington, who fine-tuned his preparations for the tournament by winning the Hassan II invitational tournament in Morocco, where he beat Darren Clarke into second place, is one of four Irish players in a field reduced to just 54 competitors.

Only the top 60 players from the money list after last weekend's Mallorca Classic were eligible to play, along with past winners to celebrate the sponsor's 20th anniversary of the tournament.

No fewer than nine players who qualified off the order of merit have not taken up the opportunity to play: Els (1st), Angel Cabrera (6th), Retief Goosen (9th), Lee Westwood (10th), Richard Green (20th), Charl Schwartz (32nd), Nick O'Hern (36th), Michael Campbell (53rd) and Anton Haig (54th).

However, the field has been augmented by four previous winners who have accepted invitations to play, two of them Irish: Paul McGinley and Ronan Rafferty, who join Harrington and Graeme McDowell in the field.

McGinley is particularly glad to avail of the sponsor's invite, as otherwise he would have missed out on playing in the Volvo Masters for only the second time since he made his debut in 1993. McGinley, whose record at Valderrama includes winning in 2005, has failed to record a single top-10 finish this season and is currently positioned 74th in the order of merit.

It is a very rare appearance on tour for Rafferty, who topped the order of merit in 1989 but who has not played since 2003, when he played 13 tournaments (making five cuts). His last competitive outing was in the Dutch Open that year. These days, Rafferty's golfing interests are mainly related to his work as a television analyst with Setanta.

Incidentally, this will be Harrington's 12th consecutive appearance in the Volvo Masters, although five of the previous appearances came at Montecastillo where he had an impressive performance rate that included one win and two runner-up finishes. It is only in recent years that he seems to have gotten acquainted with the nuances of the cork tree-lined course at Valderrama, highlighted by a runner-up finish last season which allowed him to leapfrog Paul Casey in the money race and claim the Vardon trophy.

Harrington's previous appearances at Valderrama have seen him finish second (2006), tied-10th (2005), tied 19th (2004 and 2003), tied-36th (2002) and tied-29th (1996). Although the Volvo Masters finishes the 2007 season on the European schedule, the 2008 season kicks off with next week's Champions Tournament in Shanghai where Harrington is among those playing before moving on to defend his Phoenix Dunlop tournament in Japan.

The absence of so many players, but particularly of Els, is a blow to the tournament in Valderrama and has come about because of a clash with the Singapore Open on the Asian Tour which has enticed some of the world's top players - including Els, Phil Mickelson, Vijay Singh and Westwood - to the Far East with lucrative appearance money.

Clarke is also off to Singapore, although his poor season meant he would not have secured a place in the Volvo Masters.

Still, the upshot is the quest for the Vardon trophy goes to the wire, just as it did a year ago, and with Harrington, Rose, Stenson and Fasth all mathematically in with a shout of overhauling Els, there is at least the potential for drama.