With scores going up and the number of challengers going down, anybody going double figures under par can just about count on collecting first place.

"I don't see anybody beating 12 under on this golf course," he said, adding that two rounds of 70 might be enough to hold off the elite field. "The course is only going to get tougher."

The 31-year old native of South Africa who now lives in Texas birdied six holes on the front nine in shooting an opening 67, which tied him for the lead with Paul Casey and Hunter Mahan. In the second round, he birdied three of the last four holes.

There are lots of reasons why Sabbatini's lead looks solid if he doesn't start throwing shots away.

First, low scores are hard to come by, with the second-round average of 73.049 the highest since the tournament became a WGC event in 1999. The rough is so thick and spidery that any drives missing the fairway or approaches off the green mean an almost certain bogey. Finally, the greens are getting crispy and rock hard, which will make it that much tougher to putt or to keep the ball on the green.

"It's going to be a tough weekend," said Mahan, who followed his 67 with a 73. "I guarantee you that Rory would take 6 under right now and just walk it in on Sunday. I just don't see too many guys throwing up 66 or 65 out there. Where they're going to put these pins and where we're going to have to hit the ball and the wind and everything, it's just going to be tough."

Johnson didn't find it all that difficult, at least on Friday. His 65 matched resurgent Davis Love III for the lowest round of the tournament. After an opening 71, the only blemish on his card after six birdies was a bogey on the final hole.

"This golf course, clearly I can't overpower it, and I really can't even attack it," said the reigning Masters champ. "But I can pick it apart. If I've got control of my golf ball, I can pick it apart. And today I did."