One of the first things you are ever taught about football once you start playing competitive matches, is to play to the whistle. It sounds pretty basic doesn’t it? The referee blows his whistle to start play and blows again to stop play. If you don’t hear it, well, guess what? Keep playing. Except of course if you’re Manchester United! The annual curtain raiser at Wembley between Chelsea and United was exactly what I wanted to see — two very good teams, shaking off ring rust and going at one another in an effort to lay down the first marker of the campaign. Yes, its early doors but I think we learnt a number of things about the respective clubs.Other than the glaring ‘playing-to-the-whistle,’ which won’t happen again this season if Sir Alex Ferguson has anything to do with it, United didn’t seem to have the extra gear in the new post-Cristiano Ronaldo era. Nani, who had a few good moments, looks like a cheap, lightweight replacement that still needs to evolve into a consistent Premiership performer — a dislocated shoulder will delay that even further.The pace of the Red Devils was also a concern of mine whenever Dimitar Berbatov…