Berger, who has not secured a PGA Tour victory since 2021, positioned himself for the £3m top prize after a flawless performance on the back nine, which included three birdies.
“I actually feel like I played better [today] – the course presented a slightly tougher challenge,” he remarked.
“I’m eager for the coming days and to see the challenges they will bring.”
Americans Sahith Theegala and Collin Morikawa, alongside Sweden’s Ludvig Aberg, are currently tied for third at seven under, with American Ricky Fowler trailing by one shot.
McIlroy, who birdied four of the first seven holes on the back nine, commented: “My performance on the last 10 holes was exceptionally strong.”
“Overall, I am truly satisfied. I played a very controlled and patient round of golf, which is essential on this particular course.”
American world number one Scottie Scheffler finished his round of 71 with a bogey on the 18th, leaving him at three under par.
England’s Tommy Fleetwood, who was four over after the first round, recorded three birdies on the back nine in a second-round 69, making the cut at one over.