Order of Merit leader and second seed Westwood was crushed by six holes by Indian Jeev Milkha Singh.

Singh had thought himself unlikely to play a week ago after pulling out of the US Tour event with foot trouble.

The 37-year-old described it as "a big bonus" that the lay-out this week is so vast that the players get ten buggy rides during the 18 holes.

The other winner in Group D was England's Ross Fisher, who beat Colombian Camilo Villegas by two holes.

Rory McIlroy knew facing Masters champion Angel Cabrera was a tough task on his debut in the event, even though he was the sixth seed and the Argentinian the 11th.

So it proved. Cabrera came from one down after six to win by five holes, making birdies on the last three holes and coming home in a five under 30.

"I made it tough for myself, but he just played too well," said the 20-year-old Ulsterman, "but the good thing is that I am still in it. I'm not packing my bags and heading home."

Third seed Henrik Stenson is the top man in the same group, but he looked rusty on his return from a six-week break and was beaten by three holes by in-form Simon Dyson.

"I've been struggling for a while and needed to get away from it for a bit," commented the Swede. "Maybe I needed to get away for longer, though!"

Dyson, winner of the Dunhill Links at the start of the month, won the first four holes with his opponent having three bogeys and a double bogey.

Stenson did come back from five down to two down and then lipped out from 18 feet on the 14th, but the Yorkshire golfer holed from similar range for a vital half on the next and with the victory in the bag he put the icing on the cake by chipping in for eagle at the last.

"I've been playing well for the last two months," Dyson said before turning his thoughts to games against McIlroy and Cabrera tomorrow.

The lower-seeded players amazingly won 10 of the 12 games in the day, with one other being halved, and the top four on the money list - Westwood, Kaymer, McIlroy and Casey - lost all six games they were involved in.

The action was watched by Ryder Cup captains Colin Montgomerie and Corey Pavin, although it was before McIlroy lost so heavily that Pavin remarked: "I will be shocked if he is not part of the Ryder Cup next year. He is that good."

Meanwhile, Paul Casey lost twice on his return to golf in Spain - and even with another group game still to come, he has no chance of making the semi-finals of the Volvo World Match Play Championship.

On a day of upsets at Finca Cortesin near Marbella, a very different test to the event's previous home Wentworth, the title hopes of Sergio Garcia and Martin Kaymer were ended as well.

Westwood and McIlroy may have each suffered heavy defeats - but because they played only once on the opening day, they could yet make it through to the last four.

Still troubled by the rib muscle injury which had kept him out of action since August 6, top seed Casey lost to the tournament's rank outsider Scott Strange and then to American Ryder Cup player Anthony Kim.

"Not great - I can't swing the way I want," Casey admitted after his one-hole defeat to Strange, who at 168th in the world is 164 places below the 2006 winner.

"I'm coming out of a lot of the shots. Scott played well. But having said that, I gave him three holes on the front - and you can't do that against anybody in this field."

He was three down at the turn against Kim - and even when he chipped in at the 14th, it was only for a half.

Under the old format it would have ended 3&2. But for the group stage all games continue to the 18th, and he went down by three holes.

However, Casey was a lot cheerier at the end of the day.

"This morning I was questioning whether I had come back too early," he said.

"But I don't now. That was much better - I hit a lot of good shots."

With Kim also beating Retief Goosen and then the South African getting the better of Strange, it is Kim in control of his own destiny in Group A.

He is likely to progress even if he loses narrowly to Strange tomorrow.

England's Oliver Wilson, unable to play the Wednesday pro-am after waking up with a bad neck, is in pole position in Group B after wins over Garcia and Kaymer, both by one hole.

His last group game is against Robert Allenby, who missed out on the same double when Garcia birdied the last for a half.

Even with that point, however, Garcia's match with Kaymer cannot take either to the top and Wilson will go through with a half against Allenby. Lose, though, and he is out.

"I was very nervous all day yesterday," commented Wilson, who had to pull out of the Players Championship in May with the same problem.

"I get so conscious of it and didn't sleep very well trying to stay in the right position.

"Towards the end of my first match it was tightening up, but overall it was pretty good and to win twice on the first day is everything I wanted to do.

"To beat Sergio in Spain is a really good scalp for me."