Then again, Johnson's teams do not play meaningless games, and perhaps they do not play friendlies either. Johnson's young charges had shown themselves to be the best in the NFL when winning the Super Bowl in January, and he could not bear to see them beaten - even if the result had almost no relevance to how either the Cowboys or Vikings will perform once the season starts next month. 'The coach was at least a level two on a three-point scale,' Kevin Williams, a wide receiver, said.
All of which lends spice to tomorrow's American Bowl at Wembley, when the Cowboys take on the Detroit Lions. The game will contain its usual mixture of pre-game razzmatazz, followed by a match in which most of the stars make little more than walk-on appearances. Johnson's demeanour - he hates losing - could make things a bit more competitive.
'I saw a team that has a lot of holes to fill,' Johnson said of the Minnesota defeat. 'I don't want to be an alarmist but everybody seems to be extremely happy to wear their Super Bowl rings. There's 27 teams out there waiting to take those rings. We need a sense of urgency on this team. '
Johnson, like many head coaches, finds the whole process of playing exhibition games abroad more of an ordeal than an honour, the disruption to routine interrupting the meticulous process by which plays are learnt and players evaluated. Still, as he stalked around a surprisingly physical practice at Crystal Palace this week, moving watchfully from one group to
another, it was easy to see why he is regarded as one of the best coaches in the game. His players know what is expected tomorrow.
Another participant who seemed less than delighted by a visit to London was Brett Perriman, the Detroit wide receiver, but for him the reasons were more culinary than coaching. 'The food is terrible,' Perriman had said before leaving the States. 'The hamburgers at McDonald's taste like soyabeans.' This promptly became an issue of the week and, no doubt mindful of the impact on trans-Atlantic relations Perriman later softened his line. 'I've had three meals here,' he said, 'and I've enjoyed them all.'Reuse content