No.1 McIlroy misses the cut as Kiwi Campbell leads in Hong Kong

(CNN) -- World No.1 Rory McIlroy missed the cut in his defense of the Hong Kong Open title after carding a two-over-par 72 in the second round at Fanling Friday.

It left the Northern Irish star on five-over 145 and heading home early in a rare setback in a triumphant 2012 which has seen him clinch the money list prizes on both the European and PGA Tours.

New Zealander Michael Campbell leads the way at halfway, the 43-year-old continuing his revival with a second round 64 for 131 -- nine-under-par.

Campbell reacted to McIlroy's departure with a light-hearted quip: "That makes it a lot easier for the rest of the field!," he told the official European Tour website.

The former U.S. Open champion has endured a torrid last few years, but a third-place finish at the recent Portugal Masters hinted at a revival.

He is one ahead of two-time winner Miguel Angel Jimenez of Spain, China's Zhang Lian-wei and Swede Fredrik Andersson Hed, the top four all 40 years of age or older.

Young gun McIlroy clinched the Race to Dubai in Europe last week but after a first round 73 was always struggling.

He made a good start to his second round, "I was only four off the lead at one point," he said before the shots started frittering away.

A double bogey on his final hole, four-putting the green, sealed his fate with the cut at two over.

"It was not the week I wanted but now I have got a few days to work on a few things and head to Dubai," he told gathered reporters after his round.

The concluding event of the 2012 season is the $8 million Race to Dubai which starts in the emirate next Thursday.

Meanwhile, Swede Henrik Stenson leads at halfway in the South African Open, a co-sanctioned Sunshine and European Tour event, after a 65 for 13-under 131.

Stenson is currently 59th in the Race to Dubai, with only the top 60 qualifying for the final event of the season.