Observing how athletes evolve is one of the reasons why sport makes for such compelling viewing. Charting their progress, how they develop their game or adjust to the circumstances in which they find themselves, is what maintains our interest.   It’s partly the promise of fulfilling potential and after that the exceeding of expectation that keeps us coming back, but then, when all the titles have been won and all the records broken, our attention is retained by their capacity to continue surprising us.   Eden Hazard, the 21-year-old Lille star, understands this completely.   “For me football is about conveying the pleasure that I feel when I am on the pitch,” he said. “If at the end of the game I don’t hear…