Updated

By Mark Lamport-Stokes

SAN DIEGO (Reuters) - Japan's Ryuji Imada pulled two shots clear after the third round of the San Diego Open on Saturday as some of the biggest names in the field moved into contention for a last-day push.

After sharing the overnight lead with little-known American DA Points, Imada fired a two-under-par 70 on another glorious day of sunshine at picturesque Torrey Pines to open a little daylight between himself and the chasing pack.

Although the coastal breezes strengthened in the afternoon, the 33-year-old played bogey-free golf on the back nine to post a 13-under total of 203, ending his round in style with a 34-foot birdie putt.

"The score looks pretty solid but it was a struggle out there," Imada told reporters. "I struggled with my driver today and it took me nine holes to hit my first fairway. But I battled it out with a good short game and good putting.

"I can't really let my guard down," added the 33-year-old from Hiroshima, whose only victory on the PGA Tour came at the 2008 AT&T Classic. "It's a tough enough golf course where six, seven or eight shots could change in nine holes

"I've got to keep playing well. I'm sure some of those guys are going to play really well tomorrow, so I've got to keep going, too."

Australian Michael Sim birdied two of the last three holes for a 70 and a tie for second place with American Ben Crane (69) at 11 under, a stroke in front of reigning U.S. Open champion Lucas Glover (68).

Perhaps the most significant moves of the day, however, came from three-times winner Phil Mickelson and former world number one Ernie Els.

MICKELSON LURKS

Left-hander Mickelson shrugged off a double-bogey at the par-four seventh to card a 70 and end the round in a six-way tie for fifth, just four shots off the lead.

South African Els, despite losing momentum after the turn, was a further stroke back at eight under after returning a five-birdie 69.

"My short game kept me in it," world number two Mickelson said after dumping his second shot into water at the last before getting up and down from 55 yards to save par.

"I didn't hit the ball the way I've been hitting it coming in, but I don't feel like it's far off. Hopefully I'll make an adjustment tonight.

"I'm only a few back," he said of his victory hopes going into Sunday's final round. "If I throw something in the mid to high sixties tomorrow, I think it has a very good chance."

Imada, who finished a distant second here behind Tiger Woods in 2008, dueled with playing partner Points for the lead over the front nine before taking control after the turn.

He knocked in a four-footer to birdie the 10th before rolling in his monster putt at the par-five last to snatch a two-shot cushion.

(Editing by John O'Brien)