Roger Federer has lost to Andy Murray, Mardy Fish, Andy Roddick and Gilles Simon this year other than conceding defeats to Rafael Nadal and Novak Djokovic. What has to be observed is the losses that he conceded to Fish, Roddick and Simon when, on any other day, he would have defeated them convincingly.

The latest of those defeats came from 22nd-ranked Frenchman Simon who is coming off a tournament win at Indianapolis. It could be said that he is hitting the right note in his career. Federer, after practicing for just four days after his excruciating Wimbledon final, played the Frenchman who defeated Tommy Haas, Sam Querrey and Dmitry Tursunov en route to his title.

Federer was in cruise control in the first set but a lack of concentration allowed Simon to clinch the second set 7-5. Both players traded breaks in the third and a flurry of forehand errors from Federer when he was serving to stay in the match at 4-5 handed the match on a platter to Simon, marking one of the most remarkable victories of his career.

Almost every player on the men's circuit failed to hold their serve and nerve against Federer and they subsequently lost the first set and the match. But, now that the invincibility factor surrounding Federer is gone, it's time for other players to penetrate into Federer's fragile psyche and deliver him a few more blows.

Nadal has done it in the French Open final. He repeated the act in the Wimbledon final. Should the pair meet in any of the finals on the hard courts (the US Open would be the perfect stage) Nadal will not hesitate one bit to utilise all the psychological advantage that he has gained over Federer this year.

Federer has a truckload of points to defend in the second half of the season and Nadal has to reach the semi-finals of each tournament to give Federer a run for his No.1 ranking. Nadal simply has to hope his knees hold up to displace the king from his throne, even if it's only for a brief period of time. Of course, there is always a floater called Djokovic who could throw a spanner in the works. Which half of the draw he ends up in will be the talking point of every tournament.

Federer is becoming mortal with these losses. His second-round loss to Simon at the Rogers Cup is a clear sign of choking at crucial moments for the first time in his career. If Nadal or Djokovic have any ambitions of getting the No.1 spot this year, then they have to go deep into every tournament, which will automatically put pressure on Federer to deliver the goods.

Is the teen Federer who yelled, argued and had broken rackets going to return when he starts to get pressurised? It's worth watching out for. If that happens, then the mighty cool Federer is scripting his own downfall.

If there is anyone who wants to know the turmoil that is going in Roger's head at the moment, his response to one question put to him after the defeat to Simon would have summed it up. He was asked: ''To some extent, do you agree with Justine Henin’s decision to retire at the peak of her career?''

Federer answered: ''Do I agree with that? Not today. Ask me another day. Please don’t kill me with questions like this.''