SPRINGFIELD, United States (AFP) - American Jimmy Walker birdied the par-3 12th and par-4 13th holes Friday (July 29) to seize a one-stroke lead over Argentina's Emiliano Grillo in the second round of the PGA Championship at rain-softened Baltusrol.

Walker, who fired a five-under 65 Thursday to lead after 18 holes, birdied the fifth and eighth holes and has yet to make a bogey to stand on nine-under with five holes remaining.

Grillo, who began on the back nine, birdied the 12th as well to spark a run of three birdies in four holes and birdied the par-5 18th as well to reach eight-under. With five holes to play, he also has not made a bogey in the second round.

Rory McIlroy birdied the fourth and sixth holes after going birdie-less in an opening 74 but a bogey at the ninth left the world number four three-over and beyond the cut line.

Phil Mickelson opened with a triple-bogey disaster but two front-nine birdies had the British Open runner-up on two-over and flirting with the cut as well.

World number one and defending champion Jason Day of Australia was at one-under on the day and three-under for the tournament after 10 holes. After a double bogey at seven, Day birdied three holes in a row.