Justin Rose aced the third and played solidly from then on
FIRST ROUND LEADERBOARD:
(GB & Ire unless stated)
-3 G McDowell
-2 P McGinley
-1 J Rose, P O'Malley (Aus)
Even P Harrington, R Fisher, R Jacquelin (Fr)
+1 C Montgomerie
+6 S Garcia (Sp)
+12 R Rafferty
+13 A Lyle
Justin Rose defied a stomach virus to hit a brilliant hole-in-one in an opening round of 70 in the season ending Volvo Masters at Valderrama.
Northern Ireland's Graeme McDowell (68) led by a shot from Paul McGinley.
But only four players broke par with Rose's playing partner Padraig Harrington - the pair were in the final group - finishing with a level-par 71.
The two are seeking a big finish to the year to overhaul the absent Ernie Els in the race for the Order of Merit.
Rose started brilliantly, despite being under the weather, with his first hole-in-one on the European tour.
Not only did he ace the 196-yard third with a six iron, he then birdied the fifth to go into the joint lead with McDowell as Harrington ran up a double-bogey six.
The Open champion, who came second in the event last year to pip Paul Casey to the money list crown, then dropped shots at the next two holes as well.
His five on the seventh came as a result of a penalty stroke incurred when his ball moved on the wind after he had addressed it on the green.
But he battled back superbly on the back nine with five birdies to finish level with Rose.
Afterwards, the Englishman admitted he had felt well below par throughout his round.
"I've never ached so much in my whole life," said Rose, who shares third place on one-under with Peter O'Malley of Australia.
"I picked up some sort of bug, had a bad night and was throwing up too - I'm delighted with one-under, to be honest with you.
If this wind keeps up, it's going to be a real grueling weekend
"I knew it was going to be tough out there playing last, with the wind just getting stronger and the greens drying out.
"I didn't have the energy to get frustrated out there, so that worked well in my favour."
He did appear to be flagging over the closing holes and dropped a shot at the last, almost hitting Harrington's heavily pregnant wife Caroline with a wayward approach.
Swedes Henrik Stenson and Niclas Fasth have to win the tournament to have a chance of the number one spot, but they are five and four over respectively.
Colin Montgomerie would have been joint third but for two closing bogeys, while Casey was among those who failed to break 80.
Sandy Lyle and Gregory Havret had 10s on their scorecards, Lyle when he had five air shots trying to play left-handed from the base of a tree.
McDowell said: "If this wind keeps up, it's going to be a real grueling weekend. I'm just content with the way I controlled the ball. Certainly 3-under par is beyond sort of what I was hoping for today."
McGinley was playing only because past champions, such as Lyle, were invited to mark the 20th staging of the event.
For the Irishman, a 155-yard nine-iron into the hole for an eagle two at the 16th was the obvious highlight of his day's work.