Players Championship: Jason Day four ahead despite struggles at Sawgrass

Day had four birdies, two double bogeys and a single bogey in his 73

World number one Jason Day will take a four-shot lead into the final round of the Players Championship, despite two double bogeys in a 73 in round three.

Day, 28, four-putted the sixth hole at Sawgrass on what he described as "the toughest day I've ever had to play".

The Australian played the last 10 in three under to close at 14 under, with veteran Ken Duke in a group of three sharing second.

Rory McIlroy had five three-putts in a 75 to leave him nine adrift.

"There were a few pins out there that I felt were just a little too much on the edge," Northern Ireland's world number three said.

Day's second round 66 gave him a tournament record low score of 129 at the halfway mark, but he said of the third round: "We were out there for nearly six hours today trying to play 18 holes. They made the course pretty much nearly unplayable."

After a day on which Sergio Garcia six-putted the fifth hole during his round of 77, PGA Tour rules official Mark Russell said the quickness of the greens was not planned.

"What happened was just a perfect storm with the weather," he said. "We weren't expecting a wind all day, and humidity 30%, not a cloud in the sky. They just sped up on us."

Scotland's Russell Knox had a disastrous nine on the par-three 17th, sending three balls into the water surrounding the famous island green.

"It's such an easy shot when you have no nerves or adrenaline," said the 30-year-old, who posted an eight-over 80 to drop into a tie for 40th, 13 shots behind Day.

"A pro would never miss that. We should know what we're doing. But it's a different story once you've hit two in a row in the water. The green felt like it was the size of a quarter."

Only Bob Tway, who recorded a 12 in 2005, Robert Gamez (11, 1990) and Phil Blackmar (10, 1990), have scored higher on the 17th.

Veteran Duke had no such concerns after carding six birdies in his last seven holes to surge into contention.

"A lot of Open Championships and US Opens are set up a lot harder than this," the 47-year-old said.

"We just had some wind and the greens firmed up a little bit and got speedy."

Irishman Shane Lowry, second at the halfway stage, dropped five shots in his first four holes and carded a 78 to slip back to five under alongside McIlroy.