Greg Chalmers carded a 2-under 69 to take second place at 13-under-par 200. Steve Stricker, Stewart Cink, Joe Durant, Robert Gamez, Jay Haas, Mark Hensby and Vaughn Taylor share third place at 11-under-par 202.
Weather problems on Friday forced the completion of round two Saturday morning. After that was completed, the cut of 76 players was made and round three was contested.
Coceres returned to the course Saturday morning and carded five straight pars before a birdie at the par-5 17th got him to 12 under through two rounds.
He returned to the 10th tee at TPC at Deere Run to start his third round. After three pars, Coceres rolled in a birdie try at the par-4 13th.
Coceres, a two-time winner on the PGA Tour, parred his next four holes. He then birdied the par-4 18th for the second time to get to 14 under.
Around the turn. the Argentine moved to 16 under with birdies at the second and fourth. He stumbled to just his second bogey of the tournament par-4 ninth to slip back to 15 under.
'I'm really happy, happy to share the moment with everyone and to be continuing to lead the tournament,' said Coceres. 'I'm playing very well, and I'm very thankful to all the people who have helped me to get to where I am now leading this tournament.'
Chalmers picked up one lone birdie over his final five holes of his second round. Then he opened with a birdie at the 10th and came back with another birdie at the 14th in his third round to get to minus-11.
The Australian stumbled to a bogey at the 16th. After four pars around the turn, he tripped to another bogey at the third. He recovered with strong play down the stretch.
Chalmers birdied his final two holes to get back within two strokes of Coceres.
'I started off fairly and I pretty much stayed that way the whole day up until the last two holes,' said Chalmers, who will play in the final group on a Sunday for the first time in his career. 'I'm working to win a tournament, and anything short of that, I've got to keep working. I don't know that I can sort of say, hey, this is my opportunity to win, until it really is.'
Vijay Singh, the defending champion, posted his second straight round of 67 to move to 10-under-par 203. He shares 10th place with John E. Morgan, Tom Pernice, Jr., Jeff Sluman and Jeff Brehaut.
'It was a little disappointing,' Singh said. 'I had a chance to shoot a really low number. I was 5 under through 10 holes and had good chances coming in, but just made those three bogeys, including two three-putts, a bad way to finish.'