There's been huge improvements in Federer's game since Annacone, I think at his ever ageing persona he was mentally mistaken he could continue to play a safe passive game slugging it out at the baseline. The fact was as he gets older, he would not be winning those baseline rallies.
Areas that needed work like his serve crept into his game and hurt badly all through 2009. The aggression that was once the dominant factor in his game during his prime slowly disappeared, so did his highly successful net game.
Annacone over time drastically improved Federer's serve, thats what's been key in him still reaching QF/SF/F's this year instead of R3/R4 - the variety, the timings between 1st and 2nd, not slicing back every 2nd serve etc. Clear results = WTF 2010.
World Tour Finals also showed a much more aggressive 'shortening rallies' Federer who is not afraid to attack the net. There is a big change in his net game when you compare Federer lately to him vs Berdych @ Wimbledon 2010.
Federer said in an interview sometime mid-early 2010 that he was 'frustrated where his game is' - When that happens yet you still have the passion to continue playing, that's why Federer hired a coach. A fantastic choice IMO if he still wants to be a name in 2010-2013, albeit no new slams.
