There isn't a lot to say about Roger Federer that hasn't been said already. At any rate, his record - 16 Grand Slam titles, 31 consecutive quarter-finals etc. - speaks for itself.

There are only five players on the tour who have even played in the last 31 Grand Slams, let alone reached each of their quarters.

But for all his dominance of the tennis circuit, he has never quite been able to solve the puzzle that is Rafael Nadal. Nadal holds a 17-9 record against the Swiss Master, and has won seven of their nine Grand Slam encounters. Nadal accounts for 20% of all of Federer's Grand Slam losses.

So what is it about the Spaniard's game that has Federer's measure? Is it his forehand power? Or his impossible ability to catch the lines? No, it's actually a lot simpler than that.

Nadal is left-handed.

His loopy, topspin-heavy cross-court forehand - such a basic, regulation shot - kicks up on Federer's backhand side and, as Federer uses a one-handed backhand, he can only block the ball back. Trying to hit a ball with as much spin as Rafa puts on it for a winner becomes practically impossible.

Rafa himself is not secretive about his simple tactic. He wrote about it in his book. Just pummel Federer's backhand with spin and bounce. Presumably, Federer was aware of this after just a few matches between the rivals. The fact that Nadal holds a commanding 17-9 head-to-head lead suggests there is little Federer can do to counter it.

Which brings us to tonight's match. It will be the tenth time the pair has met in Grand Slams, only the second time not in a final.

Federer has had a golden tournament so far. His second round walkover, and his relatively easy match against Bernard Tomic (in hindsight), means his physical strength hasn't been drained. The ease with which he dispatched Juan Martin Del Potro suggests he is in great touch.

He has won at least 80% of the points on his first serve in all four matches.

Nadal, too, has hardly been troubled on his way to the semis. His serve has been consistent and his winners have flowed freely. The only hiccup in his tournament was a lost tie-breaker on Tuesday night.

If I had to stick my neck and pick a winner, I'd go with Federer in at least four sets. His form is that of Federer circa 2007 and he is perfectly fit and fresh. Federer also holds a 4-0 lead in their matches indoor on hardcourt. Rafa will not make it easy, but if Federer believes he can win, he's very hard to stop.

However, the overriding sentiment falls with Nadal. Nearly all the fans and journalists from around the globe that I've spoken to in the last ten days finds Federer arrogant. Most highlighted his reluctance to acknowledge his opponent's performance when beaten. Others dislike his air of self-confidence.

Nadal, with his boyish smile and broken English, is the crowd favourite. Of course, there is still an enormous amount of respect for the Swiss Master and all he has achieved, but tennis fans will factor in your behaviour when picking sides in a neutral match. Just ask Tomas Berdych.

Over and above the ultimate result, though, the crowd tonight will want to see a ripping tennis match. Will they get the result they are after? History says probably. Will they get the match they are after? Without a doubt.