Lee Westwood has a fight on his hands to claim a 13th win in Asia and 41st of his career after seeing a commanding lead almost wiped out by Andy Sullivan in the Maybank Malaysian Open.
Westwood held a four-shot lead at the halfway stage at Kuala Lumpur Golf and Country Club and was five ahead of the chasing pack after five holes of Saturday's third round.
But the 40-year-old picked up just one further birdie and bogeyed the 18th for a round of 71 to finish 14 under par, one ahead of Sullivan who returned a superb 66.
France's Julien Quesne is four shots off the lead after a 69 containing seven birdies and four bogeys, with Westwood's Ryder Cup team-mate Nicolas Colsaerts another shot back after a 72.
Westwood looked to be in complete control when he birdied the first for the third day running, but the former world number one then missed a short par putt on the second.
At that stage he was just two ahead of playing partner Antonio Lascuna, the 43-year-old from the Philippines having birdied the first and third, but Lascuna then ran up a triple-bogey eight on the fifth as Westwood made birdie to move five shots clear.
Westwood had covered the front nine in 31 on each of the first two days but a run of pars took him out in 35 and allowed Sullivan and fellow Englishman Danny Willett to close the gap.
Sullivan had gone to the turn in 33 and also birdied the par-five 10th, while Willett was also out in 33 thanks to five birdies and two bogeys on the front nine.
A birdie on the 11th, the par three which had cost him a double bogey on Friday when his tee shot found the water guarding the green, took Westwood four clear once more, but Sullivan birdied the 12th and 16th to close within two.
And when Westwood dropped a shot on the last after finding a fairway bunker with his second shot, the destiny of the title was very much back in the balance.
Westwood admitted the extremely hot conditions had played a part in his poor finish to the round, adding: "It was tricky out there. I didn't play as well as I did the first two days, but there were some difficult flags and it was really hot.
"That's as hot as I've been on a golf course for quite some time. It was a real grind. I was leaking out there a little bit.
"You can get glazed up and lose your concentration quite easily but I'm leading going into the last round so I'm quite happy with that.
"It'll be hot again tomorrow so I'll just have to try to keep control of my swing, the ball and my emotions. It's easy to get wound up when it's as hot and humid as this."
Sullivan is looking for his first European Tour title but can draw on his experience in the Hassan Trophy last month, when he finished second after a closing 63.
"I didn't look at the leaderboard until I finished," said the 26-year-old from Nuneaton, who was part of the winning Walker Cup team in 2011. "I'll just do the same on the last day and see where it leads me.
"It was all quite satisfying. I just played good again and tried to limit my mistakes. I only made one mistake (on the fourth) but I got it back straight away. I just played really good and I'm delighted with my finish.
"I felt myself getting a bit tired coming up 15 and 16. I had a couple of sloppy swings in there but I didn't drop any shots. I holed a good putt on 16 to keep the momentum going.
"It was tough out there to keep your concentration but I'm glad my adrenaline kept me going.
"I've been playing good golf so I'll go out there tomorrow and play like how I've been playing. Hopefully I can play good golf and catch the leader."
Sullivan's 66 was the joint lowest score of the day, while former champion Matteo Manassero celebrated his 21st birthday with a 67 to finish six under.
"It's a nice birthday present for me," said Manassero, who was presented with a birthday cake after completing his round.
"It was an adventurous round, it's actually the worst golf I've played this week, but I managed to score well and I missed only a few chances for birdie and made some really good pars.
"I need to get the game back in really good shape for tomorrow if I'm going to back this round up, but obviously I'm really happy to score five under today. It's so hot today and it's hard to stay focused."