Just when Brooks Koepka appeared to have a huge advantage in the PGA Championship, along came Danny Lee

Brooks Koepka looked as if he was ready to run away with the PGA Championship on opening day. But then Danny Lee came along.

Lee, 28, who has one win in seven seasons on the PGA Tour and is ranked 119th in the world, emerged as the primary challenger to Koepka in the first round at Bethpage Black with a 6-under-par 64, putting him one stroke off the lead.

Lee hit just 10 greens in regulation but birdied eight of them, including three of the Black course's four par-3s. Of his birdie putts, none was longer than 15 feet, and five of them were from 10 feet or closer.

Lee, who began his round when Koepka was playing his second nine, heard what Koepka shot.

"I mean, have you seen him playing U.S. Opens and PGA Championships the last three years?" he said. "When you're hitting driver, pitching wedge every hole ... I wasn't surprised at all. But it didn't change my game plan at all.

"I'm not like Brooks Koepka long, but I can carry it about 290, 300 now. My mindset was honestly some kind of under-par round would be good, but obviously I did a lot better than that today, and I was very pleased with it."

Lee, who won the 2008 U.S. Amateur at Pinehurst No. 2, has made the cut in four of the nine majors in which he has competed prior to this week. In three previous PGA appearances, his best finish is 43rd, and his previous low round was a 68.

Lee was born in South Korea. His family moved in 2001 to New Zealand, where he became a citizen, and he now lives in Irving, Texas. His wife gave birth to the couple's first child last October.

"I know my family is sacrificing out there for me to chase my dream out here," he said. "I sometimes feel like I'm a bad person when I play bad because a young baby and my wife and my mother-in-law traveling with me out here, and when I don't make a good result, it just makes me feel like I didn't do what I'm supposed to do. I definitely have that kind of mindset in my head now."