Paul Casey earned a one-shot lead to take into the final round of the Valspar Championship - but could yet be left to rue Saturday's 18th hole.

The Englishman led by three from Dustin Johnson and Jason Kokrak but saw that lead cut as he dropped a shot at the last while world number one Johnson escaped from a fairway bunker to make birdie, leaving him eight under par with Casey nine under.

It was Johnson's fifth birdie of the day, offset only by a sloppy bogey at the ninth, while Casey also made five birdies including three in four holes on the back nine.

Kokrak bounced back from his only bogey of the day, at the sixth, with a birdie at the next and three more on the back nine before a memorable hole in one at the difficult par-three 15th at Innisbrook.

Kokrak told NBC: "We had 194 (yards) to carry, hit eight iron and knew if (I) flushed it, it would be perfect - and it went in like a putt."

That left him alone at seven under, one shot ahead of Luke Donald and Scott Stallings. His 66 was the best round of the day, level with Louis Oosthuizen who advanced from level par to five under.

Graeme McDowell carded a 70 and stands on level par.