Despite his inability to capture a tournament, Cink ranks seventh on this year's FedEx Cup points list and is in line to earn a spot on the American Ryder Cup team.
He shot a 6-under 64 over the TPC-River Highlands course for a two-day total of 10-under 130.
Cink was 1-over for the day through five holes when he looked at a leader board and realized he was not among the top 50 players on the course.
"That got my attention," Cink said. "I made an eagle there (at the sixth) and it was off to the races. He also eagled the 13th hole on the course where he captured his first tournament victory in 1997.
Michael Thompson, who turned professional after being the low amateur at last week's U.S. Open, was tied for fifth at 132 with Kevin Sutherland and Brad Adamonis. There were 36 players within five shots of the lead, including Kenny Perry.