Jonathan Byrd and K.J. Choi knew they were in for a tough day at Riviera Country Club, where gusting winds greeted the early starters Thursday at the $6.6 million US PGA Northern Trust Open. Byrd admitted the blustery conditions at the bluff-top home he\'s renting this week had made him \"pretty anxious\" heading into the round. But he seized the early clubhouse lead with a three-under par 68, one shot in front of South Korea\'s Choi and Brendan Steele. Choi said he knew shortly after his pre-dawn wake-up call, when he saw some palm trees bending in the wind, that conditions would be tough. Some solid putting helped make up for the vagaries of the wind, said Choi, who was pleased to hole some putts from inside five feet that he\'s been missing lately. \"The right to left wind was very hard to play against, and it made the tee shots very difficult. \"But luckily my putting was there, so I was able to recover,\" said Choi, who drained a 15-footer for birdie at the first and a 20-footer for birdie at the sixth. At nine he two-putted from 20 feet for bogey, but he regained a shot with a four-foot birdie putt at 13. Choi, who gets plenty of practice playing in the wind at his home in Dallas, Texas, said the gusty conditions were especially taxing at Riviera, where the classic layout tucked in the hills west of Los Angeles leaves little margin for error. \"What makes Riviera so difficult is the targets are very small,\" he said. \"But if you have control of what you are doing then obviously it\'s going to make it easier.\" Even so, he thought afternoon starters such as Phil Mickelson had a chance at lower scores, although winds slowed play so much that the afternoon tee times were pushed back by almost half an hour and officials opted not to send out standard-bearers with the later groups. \"I think four- or five-under par is possible,\" Choi said. \"So it was kind of a bummer not to score a little lower.\" Byrd had five birdies and two bogeys in his three-under effort. \"My approach to the golf course today was just to kind of keep it in play and have a pretty conservative game plan,\" he said. \"The hardest part was we had a lot of downwind holes today. It\'s not the predominant wind, and it was hard to stop it on some of the holes. Some of those shots are actually more difficult than into-the-wind holes.\" World number one Luke Donald, making his first US PGA start of 2012, opened with a one-under 70 that included two birdies and a bogey.