Luke Donald goes into Sunday's final round at the Northern Trust Open seven strokes off the pace but still feels he has an outside chance of victory.

The 30-year-old Englishman carded a one-under-par 70 on Saturday on a sun-splashed Riviera Country Club layout becoming increasingly difficult with the greens and fairways firming up.

"Tomorrow I'm just going to go out and play my own game," Donald told reporters after finishing the third round at four-under 209. "I don't think it (my strategy) changes too much.

"I'm in good position to have a strong finish and you never know on this course. If you can shoot four or five under, you never know what the guys are going to do ahead so you keep plugging away."

Donald, playing his first PGA Tour event of the year, expects Sunday's real challenge to come on the unpredictable, fast-running greens.

"Some of them are different firmnesses," he said. "It's very hard to predict whether they are going to release or stop. It's very hard to hit a ball very close and give yourself a lot of chances, and these greens are hard to hole putts on.

"It's a good, classic golf course. It just shows you don't really need a long, modern-day golf course to make it tough."

World number two Phil Mickelson leads the tournament at 11 under with fellow American Jeff Quinney a stroke behind.

Donald accepts he needs to go low on Sunday, and does not rule out a 62.

"It's possible," the Chicago-based professional, a double winner on the PGA Tour, said. "If you really play well and get the ball rolling in the hole, it's definitely possible.

"There are going to be some tough pins tomorrow, but you've just got to go out with that mentality that it is possible and try and do it."