(Reuters) - Jimmy Walker, one week away from the defence of his PGA Championship title, fired a five-under 65 to seize a two-shot lead after two rounds of the World Golf Championship-Bridgestone Invitational on Friday.
Walker was unfazed by a pair of weather delays totalling nearly five hours and registered six birdies and a bogey to reach the midway mark on seven-under-par 133 at Firestone Country Club in Akron, Ohio.
First-round leader Thomas Pieters of Belgium was alone in second after adding a level-par 70 to his opening 65.
Tied for third on four-under 136 were world number three Hideki Matsuyama, who posted three late birdies for 67, four-times major winner Rory McIlroy (69) and twice major winner Zach Johnson (67).
"Once we got back out there after the delay, I think everybody felt a little flat," said McIlroy. "I didn't help myself by missing a few chances as soon as we came back out.
"Luckily I found one birdie coming in," added the Northern Irishman, who chipped in for birdie at the 16th.
British Open champion Jordan Spieth shot even-par to stand another shot back with Australian Jason Day among six players bunched at 137.
Day got as low as five-under with five birdies on the front nine despite feeling a tweak in his back early in the round. He later suffered from the effects, pulling tee shots left into trees and rough, and made his way gingerly to the finish.
Walker is winless this season and has struggled since being diagnosed with Lyme disease in April. He has been unable to make an impact at the big events, finishing tied for 54th at the British Open, tied for 56th at The Players and missing the cut at the U.S. Open.
The Texan said it had been a very long day, beginning two hours early in hopes of getting done ahead of expected thunderstorms, but just what he needed.
"It did feel like a marathon, but was a great day. Played solid, hit it well, made some putts," said Walker, who has been plagued by bouts of fatigue among other disease symptoms.
"It's just important for me to have a good week. I haven't had too many this year."
Walker took the lead with a birdie following one of his trademark, high-arcing iron shots that landed two feet from the cup at the par-three 12th.
"It's been kind of rough. Things have been trending, I feel like, and hopefully it's shades of things to come," he said.
"It's still there," he said of the effect of the Lyme disease. "I still deal with it. It's better than it was, but it's still there. It affects different parts of your daily life. I just keep plugging away."
Reporting by Larry Fine in Tampa, Florida; Editing by Peter Rutherford