Shane Lowry retained the lead at the Abu Dhabi HSBC Championship but his advantage was reduced to just a solitary shot by the halfway stage of the tournament.
The Irishman tied the course record with a 10-under 62 to open up a three-shot cushion at the top of the leaderboard after the first round.
Lowry recovered from a poor start at Abu Dhabi Golf Club to stay out in front on Thursday, carding a 70 to move to 12 under through 36 holes.
A three-time winner on the European Tour, the 31-year-old bogeyed the second and third holes before making two birdies on the front nine. He picked up two more shots after the turn, while a short birdie attempt on the green at the par-five 18th narrowly failed to find the cup.
"I'm really happy with that," said Lowry. "I knew today was going to be a bit of a weird day after shooting such a low score yesterday.
"I just tried to go out and play like I played. To be honest, right from the start, I really feel like I played pretty well today. I think I gave myself a lot of chances.
"Some of the shots early on were pretty horrendous. I battled back and hit some really nice shots out there and hit some in close and made some birdies. I was happy with myself."
South African duo Richard Sterne and Louis Oosthuizen are hot on Lowry's heels, sharing second place on 11 under.
Sterne has yet to drop a shot through two rounds, while Oosthuizen matched his compatriot's four-under 68 despite bogeys at the 10th and 11th.
Early clubhouse leader Lee Westwood also signed for a 68 to sit two adrift of Lowry, with Ian Poulter, Soren Kjeldsen, Tom Lewis and Scott Jamieson a further stroke back on nine under.
Tommy Fleetwood holed a birdie put at the 18th to make the cut, but the Englishman will have to come from three under to win the tournament for a third consecutive year following a level-par 72.