Most observers are taking it as read that Roger Federer will be in his seventh consecutive Wimbledon final on Sunday. After all, his match today is his 21st grand-slam semi-final in a row; and his fiercest rival of recent years, Rafael Nadal, is not around to torment him any further.

Yet his opponent this afternoon on Centre Court is no makeweight. Tommy Haas may have never appeared in a Wimbledon semi-final before, but he has been in the top ten of the rankings for much of the past decade - though it was evident yesterday from the pitiful performance of world No 1 Dinara Safina that rankings can mean little. Haas knows Federer well, training and socialising with him, and hopes that will prove an advantage.

Since Haas suffered a shoulder injury in 2007, his results have been inconsistent as he has struggled to regain his fitness. This season, he has shown glimpses of brilliance - losing narrowly in the Australian Open to Nadal, and then allowing a two-set advantage over Federer to slip away at Roland Garros. His battling victory over Novak Djokovic in the quarter-finals, 7-5 7-6 4-6 6-3, proved that he has the style and the strength to beat the best in the world.

His coach is quietly confident but urging caution. "I don't believe that Tommy can compete against Federer from the baseline," Nick Bollettieri said. "He will probably get a little bit impatient. You've got to also remember Federer covers the court well. The key to that match is surprise attack, coming in, throwing in a few double faults on the second serve - the second serve has been winning a lot of matches with Tommy."

Federer, as generous as only the greatest player ever can be, is delighted about his friend's resurgent form.

"I've trained with him a lot, and I knew that it was just a matter of time before he started getting good results again," he said. "We've got closer recently, training then going for something to eat together afterwards. It's great when someone shows the determination to come back after injury, but I am happy the way I'm playing. I am prepared for a tough weekend ahead of me, but 21 semi-finals in a row is amazing and means the world to me."

Federer may not be talking about it too much yet, but should he lift the trophy on Sunday that will be his 15th grand slam title, breaking the record he currently shares with Pete Sampras. If he gets past Haas as expected, he will face either Andy Roddick or Andy Murray, who line up in the second semi-final later this afternoon.