Rory McIlroy still expects to win the Omega Dubai Desert Classic for the second time, despite struggling with a stomach bug as he failed to build a commanding halfway lead on Friday.
McIlroy looked back to his brilliant best as he posted a sparkling opening 63, the former world number one carding seven birdies and an eagle at Emirates Golf Club, the scene of his first European Tour title in 2009.
And although he struggled to a more pedestrian 70 on Friday, the 24-year-old's halfway total of 11 under par kept him on top of the leaderboard, one shot ahead of American Brooks Koepka, whose flawless 65 equalled the lowest score of the day.
England's Danny Willett also shot 65 to share third place on eight under alongside Ireland's Damien McGrane and France's Julien Quesne, with European number one Henrik Stenson and defending champion Stephen Gallacher among seven players another shot back after a 67.
World number one Tiger Woods, playing alongside McIlroy, could only manage a 73 to make the cut with just one shot to spare on three under.
McIlroy revealed he had felt ill during his round, although he refused to use that as an excuse.
He told the Golf Channel: "It wasn't too bad, there were a few stomach cramps. We got some takeaway food last night (Thursday) that obviously did not agree with me and this morning I was not feeling too good before coming to the course, but I don't think it affected the way I played.
"It was a little uncomfortable but it did not stop me from hitting some good shots out there and I am definitely not going to make any excuse for not playing my best today."
McIlroy dropped his first shot of the tournament on his opening hole on Friday and also hit bad drives at the next two holes, although he did birdie the par-five third and, after picking up further shots at the fifth and seventh, admitted he expected to pull away from the field.
"I thought so, yes," McIlroy told Sky Sports. "Making a few birdies on the front nine and turning two under par was a good effort, especially as the wind started to get up.
"I birdied 10, played 11 and 12 okay but then missed that little one (a par putt from inside two feet) on 13, had a chance on 15 and didn't convert and made bogey on 16, but it was nice to birdie the last and at least give myself a one-shot lead going into tomorrow.
"I will just go back tonight and regroup and realise that I am still leading the tournament. I hit a couple of loose drives which I haven't done the last couple of weeks but I still feel like I'm playing well enough to go and win the tournament."
Asked if he expected to claim his sixth European Tour title on Sunday, McIlroy added: "I do. I am leading the tournament, I've been in this position before and went on to win.
"I have led from the front quite well in tournaments that I have won. I feel like I am still playing well, I know the course as well as anyone else and I expect to go out there and shoot two good scores over the weekend and hopefully lift the trophy."
Willett began the week in unusual fashion with a charity skydive, but joked that the terrifying experience might have put golf's worries firmly into perspective.
"It was a different way to start the week, but if you are standing on the first tee trying to hit a drive on to the fairway it seems a little less nerve-racking than jumping out of a plane at 13,000ft, so it might have prepared me quite well," the 26-year-old from Sheffield said.
"As soon as you jump out you think 'What are we doing?', but after that you level out and start to feel like you are just floating down and it's unbelievable."
Koepka won "battlefield promotion" to the European Tour last season by winning three times on the Challenge Tour, his last one coming in Scotland before a quick dash to Sunningdale the next day to qualify for the Open Championship.
"I've never played with Rory, so it's going to be fun," said the 23-year-old, who shares a house in Florida with fellow player Peter Uihlein. "I know him a little bit from seeing him around, so hopefully I'll be able to play as well as I did today.
"I putted really well today. Yesterday I didn't putt very well, but today my putter came through for me. I've been striking the ball really well, and I also chipped well today. So everything's going well, I can't complain."
Woods maintained his sense of humour despite his poor round, with ESPN reporting that he joked during a junior golf clinic afterwards: "I was on so many parts of the golf course today that I got to meet so many people, signed so many autographs out there and gave a lot of balls away.
"But seriously, I was just hitting it sideways."