Let's look at the groups in detail:
Rafael Nadal: Even if he's the No. 1 player in the world, the Spaniard won't be the main favorite this year. He hasn't played a single tournament since the Asian leg of the tour. He withdrew in Paris because of the start of left shoulder tendonitis. Adding to this that the surface here is one of the least suited to him -- his results in indoor events are way less impressive than in outdoor events -- and it doesn't look good for Rafa. And let's not forget that his main weapon, the desire of winning that allows him to display all his abilities, is already turned towards the Australian Open. Anyway, he's battling in a group totally manageable for him and we all know how he hates losing. Furthermore, if he's able to get back-to-back wins, he'll be obviously become a threat for the title. Despite all of that, I don't put him on top of my list.
Novak Djokovic: Even if the Serbian is undoubtedly one of the stronger players of this latter half of the season and even if the surface suits him, he has clearly stated that both his heart and mind are focused on the Davis Cup final in a few weeks. He'll remain a serious contender, but people shouldn't expect too much from him this week because he'll be without his warrior mindset, which makes him most dangerous when motivated.
Tomas Berdych: The situation is vastly different for the big Czech than it was when he took to the court in the Wimbledon final. It can only be noticed that since that event his results look more like the ones of a top 50 player rather than a Grand Slam finalist. He tried to explain it some days ago, fully aware that his results demanded an explanation. In his opinion, he experienced issues about being thought of as a clear favorite after reaching the semifinal at the French Open and then the final in London. So, this week Tomas will be focused but his lack of confidence over the past few months should prevent him from going very far.
Andy Roddick: Andy isn't the same player anymore compared to some years ago. His results aren't consistent enough and he was weak at the majors. His best showing was making the quarters at the Australian. He showed great things in March with a more complete, varied game. His fitness was at its best too. He lost a lot of weight and seemed so eager to win. He made the final in Indian Wells and won in Miami. Since then, he's had some ups but mainly a lot of lows. He gained weight back and I've been really surprised to see how he struggles on his serve. Even if he's not complaining about it, I think he may have shoulder pain, so he's only giving his all when it's really needed and when his body allows him to. The American, who should get advantage with his serve indoors, won't be one of the main contenders at all.
In a group containing both out of shape players and players with other things in their heads, we're wondering who's going to take advantage of this: the not-really-motivated-but-in-shape ones or the motivated-ones-without-much-confidence.
Robin Soderling: Robin has just won the Masters 1000 of Paris-Bercy. He's improving again and reached the top four this week. The Swedish player would have had a huge chance to reach the semifinals in London if he hadn't been set with Andy Murray and Federer. Even with his new improved game, he's still not able to move well enough in order to beat those players. Always dangerous when he's the aggressive one, he's way more fragile when faced with players who can play very fast and who are able to read his serve. His second serves are also a good option to attack him.
Andy Murray: Here comes the second big favorite of the week. The Scotsman is playing at home in front of a devoted crowd. We know that the worst enemy of Andy is being stuck in a bad mood when things don't go as he wants them to. This "weakness" shouldn't be an issue in London because he'll be cheered on by the public, which will help him get through his frustration. As far as the game is concerned, Murray is capable of the best and the worst. Motivated and inspired, he can shine like in Toronto where he won against Federer and Nadal by playing in an amazing way. But we've also seen him sinking at the US Open against Wawrinka or for the six months after his loss in the Melbourne final. He's relying on desire and emotion. This week he'll be over-motivated and in a positive state of mind, so he'll be dangerous.
David Ferrer: The Spaniard will be the second victim of this group. This model player, always motivated, always fighting, is coming back at the top this year and the best players can lose against him when they're not at their best. But indoor and with Federer and Murray, his chances are really slim.