San Francisco - England's Paul Casey fired six birdies in a five-under par 65 on Saturday to pull away to a three-stroke lead over five-time major winner Phil Mickelson at the Pebble Beach Pro-Am.
Casey played at Spyglass Hill, one of three courses in use over the first three rounds, and after a birdie and bogey on the front nine he birdied five holes coming in.
Having started the round in a four-way tie for the lead, his 67 gave him a 15-under par total of 200 and a three-shot lead over Mickelson, who carded a two-under par 70 at Pebble Beach for a 12-under total of 203.
Mickelson, among the leaders starting the round, was even for the day through nine after three bogeys and three birdies.
After a second straight bogey at the 10th, he rallied with a birdie at the 13th, where he landed a wedge three feet from the pin, and an eagle at the par-five 14th -- where he stuck his second shot within four feet.
"I actually thought it was a successful round," said Mickelson, who said the sometimes-heavy showers made the going tough at times.
"It was difficult out there, especially around the turn there," he said. "It was very difficult but I was able to come back when it cleared up.
"I've got a good chance going into tomorrow," added Mickelson, who will be playing in the final group on Sunday for the second time in his last three starts.
Mickelson, who made his 500th career cut on Saturday, could join Mark O'Meara as the only five-time winners of the event, Mickelson's most recent triumph coming in 2012.
"I just have to play a good solid round," Mickelson said. "Obviously Paul is playing some great golf. He's going to be tough to catch."
Casey, coming off a runner-up finish in the Singapore Open in January, said that performance at Sentosa Golf Club had energized him.
"The juices were going. Because of that I'm playing better," said Casey, who was enjoying the Pro-Am experience, which can test the patience of the pros -- especially with the kind of soaking weather that has further slowed things this week.
"It's tricky on occasions, but you have to embrace it," Casey said. "The bit you can't control, the weather, you've just got to cross your fingers and hope you're at the right part of the golf course at the right time.
"It's such a joy playing these courses," added Casey, who is seeking a third US PGA Tour title. "I've always loved Pebble -- how could you not?"
Americans Scott Piercy and Lucas Glover shared third place on 204. A late bogey at Monterey Peninsula saw Glover drop from 12-under to 11-under 204 after a 70. Piercy carded a 69 at Spyglass.
Jordan Spieth, who was tied for the lead through 16 holes when rain halted the second round on Friday, returned with a late bogey to start the third round one off the pace.
He was in the hunt until two double bogeys on the back nine at Pebble Beach left him eight adrift.
Leading scores after Saturday's third round of the US PGA Tour's AT&T Pebble Beach Pro-Am tournament played at the Pebble Beach, Spyglass Hill and Monterey Peninsula courses (USA unless stated):
200 - Paul Casey (ENG) 69-64-67
203 - Phil Mickelson 65-68-70
204 - Scott Piercy 70-65-69, Lucas Glover 68-66-70
205 - Brian Gay 64-72-69, Matt Every 65-71-69
206 - Russell Knox (SCO) 68-70-68, Jonathan Byrd 69-69-68, Kim Si-woo (KOR) 66-71-69, Scott Langley 64-69-73, Rafa Cabrera Bello (ESP) 69-68-69, Jason Day (AUS) 65-69-72, Scott Stallings 67-70-69
207 - Adam Hadwin (CAN) 72-70-65, Kang Sung (KOR) 69-69-69, Chris Stroud 69-71-67, Branden Grace (RSA) 67-69-71
208 - Graeme McDowell (NIR) 68-70-70, Jim Furyk 72-68-68, Jordan Spieth 66-68-74, Martin Trainer 69-73-66