LONDON - Roger Federer celebrated reaching his 21st consecutive Grand Slam semi-final by admitting there are few players who can match his deep reserves of grasscourt secrets.

The five-time Wimbledon champion is just two wins away from capturing a record 15th Grand Slam title and having become the first man at the 2009 championship to break the serve of Croatian giant Ivo Karlovic, he left his remaining rivals in no doubt as who is the grasscourt king.

"Maybe I like to play short points. I don't mind playing one-, two-shot rallies. I also don't mind longer rallies. I think especially on grass, all my strength becomes even better. I become so much more dangerous," said Federer.

"Maybe I move better than many players on grass as well. I have a lot of experience. I think grass is a surface you maybe can't learn to play on so much and you don't get an opportunity that often, and that's why I think it's one of the reasons why it's so hard to beat me."

Federer tackles old friend Tommy Haas in the semi-finals on Friday where victory would put him into a seventh successive Wimbledon final and where either Andy Murray or Andy Roddick will be waiting.

The Swiss star admits that his record of making 21 Grand Slam semi-finals in a row is "amazing".

His last defeat before a semi-final in a major was against Gustavo Kuerten in the French Open third round in 2004.

"It means a lot to me. Just being so consistent for so long and reaching it again, it's amazing," he said.

"It's hard to believe I achieved it because it's not just I'm looking back on a few weeks or a month or a year it's really way back now.

"And even before that, I was in finals, I won a major before that as well. I just had it interrupted by Guga. But it's been quite a streak I'm on, and I'm happy it's still alive."

When Federer broke down in tears after his defeat to Rafael Nadal in the Australian Open final this year, many thought the former world number one was in a slump from which he would not emerge.

But Nadal's shock early exit at the French Open paved the way for Federer to complete a career Grand Slam by winning a first Roland Garros.

Then the world number one's injury-enforced absence from Wimbledon made Federer the favourite to regain the crown he lost to the Spaniard here last year.

"It's fun playing the biggest matches. I like playing best-of-five-set matches. And maybe this is where I'm best because everything comes out," said the second seed.

"Not only your mental strengths, but physical, tactical skills."