British golf ace Lee Westwood and Americans Kevin Chappell and Ryan Palmer are joint leader of the US PGA Championship after the England golfer fired away a six-under-par 65 on day one to be a shot ahead of world number one Rory McIlroy.
Northern Ireland's Open champion McIlroy finished with five birdies in seven holes and is in a tie for fourth with England's Chris Wood. Italy's Edoardo Molinari, American Jim Furyk and Swedish golfer Henrik Stenson are also five under par.
Defending champion Jason Dufner withdrew with a neck injury after playing his first 10 holes in eight over, while four-time winner Tiger Woods struggled to a 74, The BBC reported.
Having fired a final-round 63 in Ohio on Sunday, Westwood would now be confident of qualifying automatically for his ninth consecutive Ryder Cup, which takes place at Gleneagles next month.
And his joint lowest round in a major also put him in the frame for a first major title, having had several near-misses. Westwood said that he has played better rounds of golf but he was really pleased with the first day at Valhalla.
The Brit added that he has started to feel like his swing was coming around and also said that that 63 obviously gave him some confidence coming into this week.
McIlroy, who went out in three under par before a double bogey at 10 and a bogey at 11 at Valhalla, is chasing his fourth major title and his third tournament win in a row after victories at the Open at Hoylake and the WGC-Bridgestone Invitational last week.
Despite crashing down the leaderboard in the starting of the day, McIlroy demonstrated great powers of recovery, rattling off four straight birdies between 12 and 15 and just missing a long eagle putt at the last.
McIlroy said that he was really annoyed with his second shot at 10, which he hooked out of bounds. He said that it was actually a bit of a shock, it's the worst shot he has hit the last few weeks.
The Northern Irishman added that it came out of the blue and knocked him off track but to come back the way he did was great.
