Rory McIlroy believes shooting 67s at Quail Hollow takes "playing your a*** off", but that is his weekend goal at the US PGA Championship.
Only three players have managed to card a 67 or better so far this week, with clubhouse leader Kevin Kisner producing two four-under rounds.
McIlroy, whose two late birdies saw him shoot a 72 to be at two over and 10 shots behind Kisner, feels he will be well-placed if he can match what the American has done to begin the year's final major.
"A low round [at Quail Hollow] used to be a 61 or a 62. A low round now is a 66 or a 67. You're playing your a*** off to get that," he said.
"I'd say, if I shoot two 67s over the weekend, I'm going to have a really good chance."
Asked if he felt capable of shooting 67s, McIlroy said: "I do, for sure.
"If I drive it a little bit better than I did today, I do, yeah."
McIlroy has carded back-to-back 72s to start the tournament, leaving him with plenty of work to do over the weekend.
The four-time major winner said his tee shots let him down in the second round, while he felt the fast greens were still proving difficult.
"I thought conditions were just as tough, if not tougher this morning, as they were yesterday. I was battling," McIlroy said.
"I was scrambling well to be under par for that back nine this morning. I probably didn't quite hit it as well off the tee as I did yesterday, and wasn't putting myself in positions where I could go at a lot of pins.
"But greens are firm. Some of the pin positions are really tricky. Anything under par today is a really good score."