McIlroy has a share of the lead in Indiana after a round of 64 with Woods a shot further back, and the American admits that he was impressed by the 23-year-old.
"It's a lot of fun," Woods said after the round. "This is the next generation of guys coming out. He hits it great, putts it great, and on top of that, he's just a really nice kid. The game of golf is in great hands with him, and he's here to stay.
"I wasn't playing particularly well, but I scored.
"Rory, on the other hand, played beautifully today. Every single part of his game was working. It all looked good."
Woods and McIlroy will represent America and Europe respectively in the Ryder Cup later this month at Medinah Country Club.