Singh was at 13-under 131 on Crooked Stick, a Pete Dye course that is vulnerable to low scoring because of rain over the last several days. The second round was played early Friday to beat approaching thunderstorms, and the times were pushed back slightly Saturday to recover from whatever rain falls overnight.
"You come to a Pete Dye golf course, and you don't expect to see 13-under par leading after two days," Woods said.
He was happy just to be in the mix. For the second straight day, Woods wasn't particularly sharp in any area of his game except for posting a score.
"I didn't have it with my swing," Woods said. "Just kind of fighting it around here. You look up at the scores, the guys are just running off. I just wanted to get to double digits (under par) today. I felt like that would have been a good accomplishment the way I was hitting the golf ball, and happy to get a couple of more."
McIlroy's mistakes all seemed to cost him, whether it was a three-putt bogey or bad lies when he missed the green. He was helped by a brilliant approach on the par-5 ninth to just inside 5 feet for eagle.
"I put myself in a great position going into the weekend," McIlroy said. "The round wasn't quite as good as it was yesterday. I didn't hit the ball quite as well. But I still managed to get around in 4-under par. I'm very pleased about that. I just need to try and find a little more consistency. It wasn't that bad out there, but just a couple of missed tee shots and a couple of missed iron shots."
McIlroy and Woods are both going for a PGA Tour-leading fourth win of the year.