SINGAPORE -- Thomas Bjorn shot a 5-under 66 on Thursday to lead by stroke with half the field still yet to finish the rain-interrupted first round of the Singapore Open.
Top-ranked Rory McIlroy was at even par after eight holes when play was halted for the day due to rain and the threat of lightning.
Half the field -78 golfers - were still on the course when play was stopped. They'll resume Friday morning.
McIlroy had girlfriend Caroline Wozniacki by his side on the course. He is trying to match Luke Donald's 2011 feat of capturing both European and U.S. PGA Tour money titles in the same season.
The other big names in the field struggled. Three-time champion Adam Scott had three bogeys to go with three birdies to shoot a 71, while Phil Mickelson had a double-bogey and two bogeys on the back nine to hit a 73, one stroke in front of Padraig Harrington.
Bjorn said he adjusted quickly to the muggy conditions and the newly redesigned Serapong Course at Sentosa Golf Club, which players like Mickelson and Scott have deemed extremely challenging.
"I came here and saw the golf course and it's set up to be tricky this year," Bjorn said. "It's not the longest golf course in the world, so if you can keep it in the fairway you can produce a score, and I did that very well today. That's only round one, so we'll work from here."
The 41-year-old Bjorn is coming off a resurgent 2011 season in which he won three tournaments and finished fourth at the British Open at Royal St. George's - the scene of one of the biggest disappointments of his career.
At the 2003 British Open, Bjorn was leading by three strokes with four holes to play when his game completely unraveled. He needed three shots to get out of a bunker on the 16th hole and eventually ceded the Claret Jug to Ben Curtis.
So far this year, he's been unable to build on last season's strong results. His best finish is a share of second place at the Wales Open in June. Since then, he's only recorded two top-10 finishes on the European Tour.
Another player hoping for a boost in Singapore is Khan. He came out of nowhere to win the BMW PGA Championship in 2010 as the 471st-ranked player in the world, earning a playing exemption on the European Tour through to 2015.
The 40-year-old Englishman has found limited success since and his previously improved ranking has slipped to No. 443. He pulled out of the second stage of the PGA Qualifying School this week to compete in Singapore.
"I would love to play out there (on the PGA Tour) one day. I just feel like my form really in Europe hasn't been as good as I would have liked it to have been," Khan said. "For me, (with) a 7-year-old daughter at school, it gets a little bit more difficult. That was a consideration."
Casey, currently in 83rd place in the European Tour money list, is making a late push to make the top 60 to qualify for the Dubai World Championship. He's finishing the year strongly, with a fifth-place result at the Perth International and a sixth-place finish at the BMW Masters in Shanghai last month.
Edoardo Molinari hit a hole-in-one on the 17th en route to shooting a 70 - two days after making a rare albatross on the par-5 fourth in a practice round.
"It was funny. It does not happen very often to hole two shots like that, but at least today it counted for something," the Italian said.
The field at the $6 million tournament has been slightly weakened this year with only four of the world's top-20 golfers playing: McIlroy (1), Scott (6), Oosthuizen (10) and Mickelson (13).