Tiger Woods admits his 15th major title is proving the toughest to achieve as he looks to end the worst run of his career in golf's four biggest events in the US PGA Championship at Oak Hill.

From the start of his professional career to the 2008 US Open, Woods played in 46 consecutive major championships and won 14 of them, including his first in the paid ranks at the 1997 US Masters.

After winning at Augusta he went 10 majors before claiming his second title in the 1999 US PGA, while an identical barren run stretched from his 2002 US Open win to his 2005 US Masters triumph.

However, since the last of his 14 major titles in the 2008 US Open, the winless streak is up to a record 17 - injury prevented him from playing in the 2008 Open and US PGA and the US Open and Open in 2011 - despite five PGA Tour titles in 2013.

Asked if the 15th win was proving the hardest, Woods said: "It kind of seems that way. It's been probably the longest spell that I've had since I hadn't won a major championship. I came out here very early and got my first one back in '97.

"I've had my share of chances to win. I've had my opportunities there on the back nine on probably half of those Sundays for the last five years where I've had a chance and just haven't won it. But the key is to keep giving myself chances and eventually I'll start getting them."

The last of those chances came in the Open at Muirfield last month, where he was two shots behind leader Lee Westwood going into the final round but struggled to a closing 74 to finish five shots behind winner Phil Mickelson,

On his next appearance the world number one shot a second round of 61 on his way to a seven-shot victory in the Bridgestone Invitational - his eighth win at Firestone Country Club - and insisted today only his putting was the difference between the two.

"Obviously I feel pretty good about winning by seven and coming here," Woods added. "I feel like my game's pretty good. That's how I played at the British Open. Only difference is I made more putts last week.

"I think winning one major championship automatically means you had a great year, even if you miss the cut in every other tournament, you're part of history.

"I think it's been a great year so far for me, winning five times and you look at the quality of tournaments I've won, a Players (Championship), two World Golf Championships in there, that's pretty good."

Woods finished 39th the last time the US PGA was played at Oak Hill in 2003, at the time his worst finish in a major as a professional, but still labelled the course in upstate New York as the toughest and fairest he had ever played.

"Absolutely (that still stands)," the 37-year-old added today. "It has always been fair, it's just tough. The rough is up, the fairways are perfect, greens are getting up to speed now. It's just a very difficult golf course."

Woods just chipped and putted on the front nine on Monday but resumed his early morning major routine on Tuesday, playing the back nine in splendid isolation after teeing off at 6:22am.

He was prevented from starting so early at Muirfield last month, being forced to follow the rules which stated that the course was not open until 7am after attempting to tee off 10 minutes early.

The tendency to practice so early has annoyed paying spectators in the past if they arrived at the course to find Woods had already gone, but yesterday did provide an insight into the problems which can be caused by large crowds.

Woods was trying to sign autographs on his way to the driving range when a fence almost collapsed under the weight of people, while a similar incident occurred today.

"They almost knocked the fence down. It gets dangerous," Woods said. "We had a little girl get crushed today and she was just on the ground crying. People get so aggressive for autographs and security is trying to be aggressive to protect the little kids up front.

"You try and sign, but sometimes the adults start running over the little kids up front, and especially on a fence like that, on a hard fence, it can get dangerous sometimes."