PINEHURST, N.C. (AP) — Martin Kaymer is turning the U.S. Open into a rout, and it's not even the weekend.

On a warm, sunny morning at Pinehurst No. 2, Kaymer piled up five more birdies during the second round Friday, taking his score to 10 under for the tournament. He went to his 15th hole of the day a staggering eight shots ahead and challenging the record for the lowest 36-hole score in a major.

Kaymer opened the tournament with a 5-under 65, the lowest score in three U.S. Opens at this historic course in the North Carolina sand hills.

The 29-year-old German had 11 birdies and just one bogey through his first 32 holes.

Dustin Johnson and Brendon de Jonge were on the course with 2-under scores. Graeme McDowell and Kevin Na, who had 2-under 68s in the opening round, were scheduled to tee off in the afternoon. So is Phil Mickelson, a runner-up at the U.S. Open a record six times but never a winner. Lefty opened with a 70 in his pursuit of the title he needs for a career Grand Slam.

The course was saturated with overnight storms, making the perilous greens very inviting for those fortunate to have an early tee time. That included Kaymer, who is riding the confidence from his victory at The Players Championship last month.

But Kaymer dazzled even before the rains came. He seized the lead with three birdies on the final five holes Thursday.

"It's a good round of golf. I wasn't expecting it. I'm not freaking out about it," he said. "A good start, but that's it. There's nothing more than that. If other people want to make more out of it, it's fine. For me, it's just a great start into one of the most important weeks of the year."

Kaymer joined the exclusive major club with his victory at the 2010 PGA Championship, but a swing change shortly after the biggest win of his career took longer to take hold than expected. He went through a winless drought that would eventually stretch to 29 tournaments over 18 months.

Then came Kaymer's performance at TPC Sawgrass, where he tied the course record with an opening 63 and held off one of the strongest fields of the year to capture a title that brings nearly as much prestige as a major championship.

"I needed a win," Kaymer said. "Whether it was The Players or a regular PGA Tour event, I just needed it for my confidence, for all the hard work I've put in the last couple of years."

Pinehurst has been playing easier than expected. Fifteen golfers shot in the 60s during the opening round — the most since there were 24 at Olympia Fields in 2003.

Look for the course setup to get much tougher heading into the weekend, though the heavy rains made it difficult to put some bite in Pinehurst.

"There's a long way to go," Na said. "At the end of the tournament, even par is going to win this championship."

Not the way Kaymer is playing.

___