PONTE VEDRA BEACH, May 9, 2014 (AFP) - Germany's Kaymer, whose first-round 63 matched the tournament record and included a TPC Sawgrass record front-side 29, stood on 12-under 132 after 36 holes.
"I see very positive things that I backed up nine-under par with another decent round," said Kaymer.
Spieth, the 20-year-old US prodigy who contended at last month's Masters, is bogey-free through the first two rounds after a 66 to finish on 133 with fellow American Russell Henley third on 136.
"I'm very happy with the way I'm striking the ball," Spieth said.
Englishman Lee Westwood and his countryman Justin Rose, the reigning US Open champion, shared fourth on 138 with Spain's Sergio Garcia and Americans Gary Woodland and Jim Furyk.
Kaymer, who won his first major title at the 2010 PGA Championship, hit only six of 14 fairways -- half as many as Thursday -- but remained solid with his irons and putter.
"I didn't hit as many fairways as yesterday, but I managed my way quite nicely around the golf course, had a couple of nice up-and-downs, two longer putts went in," Kaymer said. "So I think I kept it really well together and kept myself in the tournament."
The 29-year-old from Dusseldorf sank a 28-foot birdie putt at the par-3 third and responded to a bogey at the seventh with a five-foot birdie putt at the par-5 ninth.
Kaymer followed with a 12-foot birdie putt at the 12th, found the rough and a greenside bunker at 14 on the way to a bogey, but answered with a 30-foot birdie putt at 15 and a five-foot birdie putt at the par-3 17th.
- Scott makes cut on the number -
Adam Scott, one of four players who this week can overtake injury-idled 2013 Players champion Tiger Woods for the world number one ranking, fired a 67 Friday to make the cut on the number at level par 144, sharing 64th.
A nightmare 77 for the second-ranked Australian in round one nearly doomed the 2013 Masters winner's bid to topple Woods, with a top-16 finish needed to achieve the feat.
"I think my game is pretty good, but certainly at Augusta and then kind of here, as well, my pace putting has been poor, and it's a big momentum killer," Scott said.
"All of a sudden I'm putting it in reverse again. Just need to sharpen that up. That's the only thing that I'm going to be really critical on my game with. Anything outside 10 feet or even six feet, I just don't have a good chance."
Swede Henrik Stenson, the 2009 Players winner who needs a top-six effort to take the top spot, fired a 70 to stand on 141, sharing 25th.
American Bubba Watson, in his first event since capturing his second Masters title last month, shot 72 to join Stenson on 141.
Watson, who must be second alone to have a chance at number one, is off to his best start in seven Players appearances. He has never finished higher than 37th in the event.
American Matt Kuchar, the 2012 Players champion who must win to have a chance at number one, fired his second 71 in a row to stand 10 behind Kaymer, sharing 37th on 142.
Phil Mickelson failed to reach the weekend, the reigning British Open champion missing the cut on 145 after a 70 Friday. The US lefthander will try to complete a career grand slam at next month's US Open at Pinehurst, North Carolina.
Scores on Friday after the second round of the $10 million US PGA Players Championship (par 72, USA unless noted):
132 - Martin Kaymer (GER) 63-69
133 - Jordan Spieth 67-66
136 - Russell Henley 65-71
138 - Jim Furyk 70-68, Lee Westwood (ENG) 67-71, Gary Woodland 67-71, Justin Rose (ENG) 67-71, Sergio Garcia (ESP) 67-71
139 - Brian Davis (ENG) 72-67, John Senden (AUS) 70-69, Bill Haas 68-71, Bae Sang-Moon (KOR) 66-73, George McNeil 71-68, Geoff Ogilvy (AUS) 69-70, Matt Jones (AUS) 70-69, Kevin Na 70-69, Charl Schwartzel (RSA) 72-67, Scott Brown 68-71
140 - Freddie Jacobson (SWE) 70-70, Kevin Chappell 72-68, Joost Luiten (NED) 69-72, Zach Johnson 69-71, Graeme McDowell (NIR) 69-71, Stewart Cink 70-70