Vijay Singh claimed the halfway lead in the BMW Championship, but European Ryder Cup stars Rory McIlroy and Lee Westwood were firmly in contention at Crooked Stick.
Fijian veteran Singh carded a 66 to reach 13 under, putting him on course for a first PGA Tour title in four years.
McIlroy, Tiger Woods and Ryan Moore were one shot back, with Westwood alongside Bo Van Pelt at 11 under following a superb 65.
McIlroy was unable to repeat his stunning opening day performance, which earned him a share of the lead.
The World Number One still recorded six birdies and an eagle, but also ran up four bogeys en route to a 68.
"It wasn't as good a day as yesterday," he reflected. "I didn't hit the ball quite as well, but scored well and did enough to go out there and shoot another good number and set myself up in a good position going into the weekend.
"I could have hit the ball a little better from tee to green, but I still got it around in four under, so pretty happy.
The 23-year-old, leader of the FedEx Cup standings, added: "I just need to try to 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."
Woods overcame some disappointing drives to pick up shots on five holes, including the last two, while Westwood started his round with back to back birdies and continued to prosper as the day wore on.
Two other members of José María Olazábal’s European Team, Graeme McDowell and Ian Poulter, were well placed in Indiana.
McDowell shot 67 to move to nine under, while Poulter was one worse off after a second successive 68.