* Englishman going for repeat win
* Once enjoyed three-stroke lead
* Kokrak has hole-in-one at 15th (Adds details, quotes)
March 23 (Reuters) - Defending champion Paul Casey held on for a one-stroke third-round lead over world number one Dustin Johnson at the Valspar Championship in Florida on Saturday.
England’s Casey shot 68 to top the leaderboard at nine-under 204 but what had been a three-stroke lead had dwindled to one at the end of the round.
“I was patient for the most part and aggressive ... when I had opportunities and game felt really, really good,” said Casey, who is seeking to become the first back-to-back winner in the 19 years of the event.
“Looking forward to tomorrow, playing with Dustin is going to be very exciting,” said Casey. “Any time I got a chance to go up against world number one I’m excited about that.”
Johnson applied the pressure with a 67, including a birdie at the last, and fellow American Jason Kokrak (66) was close behind on 206, thanks in part to a hole-in-one at the par-three 15th.
England’s Luke Donald and American Scott Stallings were also in contention after both shot rounds of 70 to finish on 207.
Casey gave himself some breathing room after picking up three shots on the back nine but ended the round on a downer with a bogey at the last.
Johnson also had five birdies but only one bogey and he put on a show with his birdie at the 18th.
“I had a good lie in the bunker, but it was on an upslope and had to get it over the lip so I had to hit it really high,” he said. “It was into the wind, up the hill, only had 130 yards I think.
“I hit a full nine-iron and ... luckily I made really good contact with it and it flew just past the hole.”
But the birdie putt was a challenge.
“Even then I had whatever, seven feet, and still had a big swinging downhill putt,” Johnson said.
“I mean these greens are really fast but a lot of slope on them. Sometimes you hit them really close you don’t have easy birdie putts.”
The ace was the second of Kokrak’s professional career.
He used an eight-iron on the 212-yard hole.
“It (the ball) carried just far enough and took a nice hop and rolled in there,” Kokrak said.
Reporting by Gene Cherry in Raleigh, North Carolina, editing by Ed Osmond/Peter Rutherford