Luke Donald is on course to regain his world number one status after taking a two shot lead into the final round of the BMW Championship at Wentworth.
The Englishman, who needs a top-eight finish to take Rory McIlroy's top spot in the rankings, shot 69 for 11 under ahead of countryman Justin Rose (69).
Ireland's Peter Lawrie was seven under with Ernie Els five under.
Two more South Africans, Richard Sterne and Branden Grace and Scotland's Paul Lawrie were also five under.
Defending champion Donald was a model of calm despite the blustery conditions and carded one birdie and eight pars in an opening 34 before three further birdies, marred by just one bogey at 15, on his way home.
"Mentally and physically it was very tiring," he told BBC Sport. "This was a tough day, the wind was blowing and this course is not easy in good conditions. I really had to focus hard."
Donald beat Lee Westwood in a play-off last year to become world number one for the first time and looks on course to return to the head of the rankings after McIlroy missed the cut on Friday.
"If all goes well and I win the world ranking takes care of itself," said Donald, who will play with Rose in the final group. "It would be a proud moment to go a whole year and have the world ranking. It's special but obviously the focus is to go out and try to defend the tournament.
"I played with Justin the first two rounds and he's swinging nicely. It's going to be a good battle. I'm excited."
Donald would join Sir Nick Faldo and Colin Montgomerie as the only players to make a successful defence of the European Tour's flagship event.
Rose, who could move to a career-high fifth in the world by winning, said: "It was one of those where I didn't realise how good a round it was until I saw that the course had taken its toll.
"There were some borderline holes, as there are at US Opens and on Sundays, but I sort of relished the challenge.
"It takes all your experience and patience and it certainly tested me."
Els, who has overseen a number of changes to the West Course in recent years, was highly critical of Tour officials after his round for what he perceived to be a lack of watering that rendered many greens too firm.
Englishman Ian Poulter carded the joint lowest round of the day with Donald and Rose to climb to three under and a tie for 11th. Compatriot Lee Westwood, the world number three, took 70 to end one under.
England's James Morrison, who held a four-shot overnight lead after a sparkling 64, struggled early on and made a triple-bogey eight at the fourth and a quadruple-bogey eight at the eighth to plummet down the leaderboard.
The 27-year-old world number 236 steadied the ship with four pars before swapping a bogey and a birdie on the way home to end three under after an 81.
"With the wind and the firmness of the course it was brutal," he said. "I'm very, very disappointed but it's definitely a learning curve for me."