Manchester City captain Vincent Kompany proves his worth as greatest buy of all Ferdinand, in his prime, was phenomenal, but I believe that Kompany might just have the edge on the United defender. When I look at his game, I cannot see a weakness. Manchester United manager Sir Alex Ferguson claimed that Kompany had a habit of diving into tackles, after he was sent off for a challenge on Nani during the FA Cup tie at the Etihad in January, but I don't agree with that. My initial reaction was that Kompany had made a perfect tackle and was unlucky to be sent off, but it happened at a time when referees were clamping down on such challenges. Had it happened last week, Kompany would have stayed on the pitch. But he does not dive in, he stays on his feet. One of the biggest compliments that you can pay to the Belgium international is that he has become so impressive at centre-half, despite starting out as a midfielder. I have always been sceptical about midfielders dropping back into defence because playing in the back four is all about three things - positioning, positioning and positioning. The man on the street might not look at it like that, but the secret to being a good defender is knowing about where to be and when to be there. Most defenders gain that knowledge through years of experience. I remember when people used to talk about Bryan Robson and Glenn Hoddle being good enough to drop back from midfield to play as a sweeper, but I always viewed that as nonsense because they wouldn't have that crucial sense of positioning. Matthias Sammer managed it for Germany at Euro 96, but he was pretty much an exception, yet Kompany has now gone from playing in midfield to establishing himself as a top-class centre-half. The good news for City is that, at 26, he is only likely to get better and better. He is approaching his peak. I had two spells in my career when I felt I was at the very top of my game. The first was when I could run and bring the ball forward and I was 29, in the 1984-85 season, when I was at that first peak. Then I lost my pace and became a better defender at 31 because I began to benefit from my experience, but Kompany still has great pace and his positional sense is excellent. We really haven't seen the best of him yet, but the only thing that he has to worry about is injury. Injuries have now beaten Ferdinand and taken away the best attributes he displayed during his prime, while Terry has also been hit by fitness problems. Vidic has also been sidelined this season by a cruciate ligament injury and his loss has been a terrible blow for United. Last season, Vidic and Ferguson were the two reasons why United won the Premier league, but when you look to pinpoint crucial factors in City's title triumph, you look at Yaya Touré and Kompany. On top of his defensive attributes, Kompany has also proven to be the perfect captain, so nobody deserves to the lift the league trophy more than he does. Finally, a word on City manager Roberto Mancini. I've not been his biggest fan but he did what was asked of him on Sunday - on the biggest day of all - and gave City their lifeline when it mattered by bringing on Edin Dzeko. It set up that incredible final five minutes of added time and I already fancy City to retain their title next season.