As Manchester City and Chelsea learned the hard way, concentration is required until the very last momentSome football managers talk a lot without saying very much. Alex Ferguson is not one of them and words he uttered nearly 20 years ago came to mind this week as first Manchester City then Chelsea threw away potentially match-winning leads in the Champions League. When Manchester United entered the Champions League, which had replaced the European Cup, for the first time Ferguson offered this caveat: "In Europe, just when you think you've cracked it, that's when the roof falls in."Presumably City and Chelsea would go along with this having e...