Turns out the problem was the equipment, not the golfer.
DiMarco noticed during a practice round that his putter's grip was bent about 30 degrees. He straightened that out, and was 8-under after three rounds.
'I was just out here, trying to figure out what was going on,' he said after shooting 67 on Saturday. 'I looked down at my grip and saw it was bent.'
DiMarco thinks the putter got bent on the way back from the British Open. After finishing second at Hoylake, he missed the cut at the Buick Open and International.
'The last two weeks,' he said, 'I missed a lot of putts to the right.'
In the past, Geoff Ogilvy might have crumbled after a start like this. Instead, the reigning U.S. Open champion remains in contention, three strokes off the lead.
Things didn't look good when he missed a 6-foot putt and double-bogeyed the first hole. But he eagled the No. 5 and shot 4-under for the day.
'I might not have fallen apart and had hundreds, but I don't know if I would have come back as well as I did,' Ogilvy said. 'In a major that's a pretty disappointing thing -- you sit there all night, thinking you're in contention and ... you drop two shots on the first hole. It feels like you're dropping three shots, really. Yeah, it wasn't a fun way to start.'
MAYFAIR'S MOM IMPROVING
Billy Mayfair said his mother was alert after suffering a heart attack and stroke earlier in the week.
'She knows I'm playing in the tournament, and she still thinks she's at home, but she's in the hospital and that's OK,' he said. 'Her vitals are getting better.'
Billy Mayfair, meanwhile, is at 5-under despite a tough couple of weeks. He underwent cancer surgery about two weeks ago after finding a growth in his testicles.
A RYDER PUSH
A two-way tie for seventh most likely would put Tim Herron on the U.S. Ryder Cup team. He is in a four-way tie for eighth at 8-under.
'You think about it when you're away from (the course), but when I step on the tee, I've just got to play golf,' Herron said. 'That's all I can do.'
ANOTHER MEDINAH MOMENT?
At 10-under and tied for fifth, it will take quite an effort by Sergio Garcia to catch the leaders.
He has a good history at Medinah, though.
Garcia delivered a memorable moment, with his shot from the base of an oak tree to the green on the 16th hole in 1999. Playing in only his second major as a pro, Garcia wound up runner-up to Tiger Woods, losing by one stroke.
'I guess I do like the course,' Garcia said. 'I've done well on it, (but) I don't know whether I can do it. I've been playing well all week. That helps.'
Luke Donald and Tiger Woods share the lead at 14-under.
LOW SCORES? NO PROBLEM
There are six players 10-under par or better. To those who think the parade of birdies diminishes the PGA Championship as a major, Phil Mickelson offered this rebuttal.
'I would disagree with them,' he said.
'Because I think they're wrong,' Mickelson said.