LONDON (AFP) - Roger Federer admitted he was delighted to be at the centre of a Wimbledon old boys reunion after reaching his 21st Grand Slam semi-final on Wednesday. Federer eased past big-serving Croatian Ivo Karlovic 6-3, 7-5, 7-6 (7/3) as he stayed on course for a sixth title and a record 15th major. The Swiss star, who will be 28 in August, now faces 31-year-old German Tommy Haas for a place in the final. Lleyton Hewitt, 28, was facing 26-year-old Andy Roddick in one of Wednesday's other quarter-finals although age caught up with 29-year-old Juan Carlos Ferrero who lost to Andy Murray, seven years his junior. "I'm very happy that so many of the guys have made it through to the second week and the quarter-final stages and we'll have Andy or Lleyton going through," said Federer."Then also Ferrero. I'm very happy he's come a long way again, because sometimes he gets forgotten next to all the hype in Spain with Rafa."It's fun to see also Tommy around after injury. I like a good mix because it's not always just the young guys and me. "It's cool once in a while, but I still like to play the guys also who I used to play when I came up and who were my main rivals for many years. It's really exciting."Federer also defended Karlovic's style of play that's based on a booming serve which saw him send down 137 aces in four matches before Wednesday and face just four break points. "It's not fair to call him boring. He's got a phenomenal serve. The way he backs it up with his volleys, it's quite something. I think it's exciting actually to go see him play," said Federer. "He still got 23 aces. You get maybe just a couple chances a match but I'm there and I know I will believe in it. The opponent knows it, too. I'm trying to make it as difficult as possible for my opponent. "I think this is where I might have the edge over some other players." Federer broke the Croatian twice in the match at key points to lead 3-1 in the opening set and to lead 6-5 in the second. The 6ft 10in (2.08m) Karlovic, playing in his first Grand Slam quarter-final, blamed the pressure of the occasion, the identity of his opponent as well as the bright sunshine for having his defences breached. "He returned unbelievably and I couldn't really react because of the sun was in my eyes," said the 30-year-old who quickly grabbed a pair of sunglasses from his bag at courtside. "He is better than everyone else, that's why he could break my serve. I couldn't do anything about it. "He was unbelievable in the first two sets. He didn't give me any chances. In the third set his level went a little bit down and I started to play better." Karlovic believes that the Federer second serve is there to be attacked despite winning just 11 points off the Swiss star's serve in the entire match. "But he is the best player on grass by far. The ball here jumps up just to his waist and that suits his style," he said.