Andalucia Masters first round leaderboard:
-5 P Larrazabal (Sp) -3 G McDowell (NI), D McGrane (Ire) -2 G Maybin (NI), S Kapur (Ind)
Selected others:-1 S Garcia (Sp), MA Jimenez (Sp) level R Fisher (Eng) +1 M Kaymer (Ger), D Clarke (NI), T Bjorn (Den) +2 JM Olazabal (Sp) +3 P McGinley (Ire)
Kaymer's playing partner McDowell can close the gap in the Race To Dubai
Martin Kaymer's bid to become world number one began quietly as he shot a one-over 72 to trail by six shots after the first day at the Andalucia Masters.
The 25-year-old German needs to finish in the top two in Valderrama this week to end the 281-week reign of Tiger Woods but had four bogeys in his round.
Should he not finish in the top two the absent Lee Westwood, resting a calf injury, would replace Woods at the top.
Spaniard Pablo Larrazabal leads by two from Graeme McDowell after a fine 66.
Kaymer secured the Rookie of the Year title in 2007 after finishing sixth in the Volvo Masters, which was also played at the picturesque Valderrama course.
He struggled at times on the 6,988-yard par 71 lay-out on Thursday, however, dropping three shots in succession from the 11th.
But he hit a huge drive down the well protected 433-yard 16th and pitched to two feet for his third birdie of the day.
Kaymer was phlegmatic after his round and said: "It wasn't that bad a round and it's not the end of the world."
The German leads US Open champion McDowell by almost a million euros in the European Tour money list, the Race to Dubai, and said: "I've got a lot to think about.
"So it's important on this course not to give up. You have to stay patient and that's what I did after making three bogeys."
With half a million euros on offer to the winner this week, McDowell admitted that he needs to be challenging for victories in order to put pressure on his Ryder Cup colleague at the top of the list.
Kaymer drives at the fourth hole on the magnificent Valderrama course
"I need to have some strong finishes if I'm to catch him. It's not as if I'm only 10 or 12 thousand euros behind him," he said.
"Martin didn't have his best day today but he's never far from his best. I had a couple of key saves on the front nine, I think bogey-free is exceptional at Valderrama."
Irishman Damien McGrane joined McDowell at three under after making a birdie at the final hole.
The 39-year-old, without a victory since his maiden European Tour title at the 2008 China Open, is currently 53rd in the Race to Dubai with five top-10 finishes from his 27 events this season.
Meanwhile, Sergio Garcia, the former world number two who has slipped to 69th in the world rankings in less than two years, returned a respectable 70, with five birdies and four dropped shots.
But Larrazabal secured his useful advantage after birdies at the 16th and 17th.
The 27-year-old Spaniard, who won the 208 French Open, currently languishes in 85th place in the money list after only three top-10 finishes in 28 Tour events, with a best of third at the BMW International in Munich in June.