Padraig Harrington said there was still room for improvement in his game after securing his third victory in the last six majors.
"Do I believe I can improve as a player? Yes," the 36-year-old Irishman told reporters on Monday after winning the U.S. PGA Championship by two strokes at Oakland Hills on Sunday.
"There's plenty of my game to improve."
Harrington putted superbly down the stretch to seal his second successive major title on one of the toughest layouts in the game, doing so in the manner of world No. 1 Tiger Woods as he almost willed the ball into the hole.
The Dubliner has joined Phil Mickelson, Ernie Els and Vijay Singh as a triple major champion and is perhaps the likeliest of that quartet to accumulate more.
"I have probably been the leading player in Europe for close to six years," said Harrington after becoming the first European to win the PGA Championship since Scotland's Tommy Armour in 1930.
Renowned for his workaholic approach, Harrington has always been a keen student with a yearning desire to improve.
"I am maturing as a player," said the winner of the last two British Opens.
"Throughout my career I've always applied myself, looked for what would improve my game, found that and worked on it to improve.
"It is a long way to catch Tiger at the top but I know the only way of focusing on doing that is focusing on me, what I'm doing, controlling what I can do. I can't control Tiger or Phil."
Woods has missed the last two majors after being sidelined for the rest of the year following reconstructive knee surgery in June.
Harrington, a 14-time champion on the European Tour, said he first knew he was capable of winning a major after slipping to fifth in the 2006 U.S. Open at Winged Foot.
The Irishman was one of several players who squandered victory chances over the brutal closing stretch, bogeying the last three holes to finish two strokes behind winner Geoff Ogilvy of Australia.
"I probably pushed too hard on the 17th hole, thinking I needed to get back after making my first bogey of the day on the 16th," said Harrington.
"But I walked away from that tournament knowing I could win a major. Sometimes you've got to lose them to know you can win them."