(CNN) -- Graeme McDowell admitted he had been "left in the dust" by European Tour money leader Martin Kaymer in the first round of the season-ending Dubai World Championship on Thursday.
The U.S. Open champion, like Kaymer seeking to win the Race To Dubai title for the first time, was five shots adrift of the German after carding a par 72.
His playing partner Kaymer, who can end Lee Westwood's short run as world No. 1 if he takes home the $1.2 million winner's purse, came out of the blocks running as he fired a birdie at his second hole and then an eagle two at the third.
They were upstaged by Sweden's Robert Karlsson, the European No. 1 two years ago, who shot an up-and-down 65 which featured an eagle, eight birdies and bogeys at his first ninth and final holes.
That six on the 18th meant that the 41-year-old, who missed half of last season with an eye problem, ended the day just one shot ahead of South Korean teenager Noh Seung-yul as the 19-year-old signed for a flawless 66.
Thailand's Thongchai Jaidee was fourth on 68 while Westwood -- still recovering from a calf injury -- was tied for fifth on 69 in a group including Sunday's Hong Kong Open champion Ian Poulter and Spain's Sergio Garcia.
McDowell, tied for 25th after carding three birdies and as many bogeys, said Kaymer had won their initial battle.
"It frustrated me a little bit playing with him because he was playing so well," the Northern Irishman told the European Tour website. "He kind of left me in the dust literally out there, so it's great to get away from him and the distraction tomorrow.
"In the morning there will be a little less grain on the greens and they will be a little less scuffed up. It should be a good chance to make some putts.
"He's a pretty emotionless guy and would be a helluva poker player. He's a cool customer -- there were no signs of any nerves and I was very impressed."
Kaymer leads McDowell by $380,000 and can afford to finish as low as 52nd in the 60-man field if his Ryder Cup teammate ends the week tied for third or worse.
The U.S. PGA Championship winner was delighted after sinking a 192-yard seven iron at the third hole.
"I think the last time I holed out from the fairway was on the [second-tier] Challenge Tour. I never got that lucky, but it's the right week -- the most important of my career so far -- to get lucky," he said.
If Kaymer wins, Westwood must finish at least tied for second to keep the No. 1 ranking he took from Tiger Woods at the end of last month, then held onto with a runner-up effort at the HSBC Champions event in China.
"Everybody's got to remember I'm still rehabbing. I've not been able to work on my game and it does not help that it's as hot as it is -- it makes it swell," the Englishman said.
"I'm hoping it'll be back to 100 percent next season and I'm looking forward to not having to worry about it. I showed I was rusty and was not competitive sharp, but I hit only two iffy shots all day. I've played once in the last five weeks."