Why do footballers need a rest?

I was scanning through the sports headlines on the BBC website and saw Jose Mourinho's comment about resting players at the weekend."The players that have accumulated lots of minutes are not going to play next weekend," he said. But what constitutes "lots of minutes"?

If a tennis player wants to win a grand slam they have to play 7 matches in 14 days and spend time on the practice courts too. A men's match might last anywhere between 2 and 5 hours, the women spend anywhere between 1 and 3 hours on court. The tennis season is also very long. Most top players will play around 20 tournaments a year. Getting through only 2 rounds each time would mean 60 matches.

So I'm perplexed. A tennis player has to give full commitment and concentration throughout the match. They don't' have a team around them to cover for any momentary lapses in concentration. So there must be something different that means a footballer can't cope with a heavy schedule. Is it recovery, fitness or what? I'm not suggesting they are somehow less of an athlete or poorly conditioned for their sport. I'm just wondering what makes one person able to sustain the effort and concentration required over an intense and focussed schedule of games and another not being able to do so.

Perhaps the fact that tennis is focussed on a much smaller area compared to a football pitch changes things, or the simple fact that you are only playing against one or two other people rather than eleven takes a different toll on your mental resources.

The bottom line is that you can't compare apples and oranges and so the difference between a footballer, a racquet sports person, a rugby player or a triathlete is an unrealistic comparison. The demands of their chosen sports must have an impact that differs from sport to sport.

Today's sportsman or sportswoman is more highly trained, better conditioned and better prepared. As a result the sport they play is more physically and mentally demanding. It's faster and as a result more intense. Perhaps this is why resting players is more common.