Listened to 606 and I am not Mills' biggest fan to put it lightly, but thought he did not say much wrong. Chelsea matches are more expensive than the England vs Slovenia game. International is the highest level and the world cup shows it. Lazy players like Ruiz giving everything, CL winners like David Luiz and Marcelo collapsing under the pressure etc.
As for tennis, that's definitely a sport football does not want to be copying when it comes to tiredness. Apart from Agassi (who took a year off in his early days and rarely trained and Lendl every tennis great in the last 30 years has decline dramatically at 27. Even Federer declined greatly at that age and he managed his schedule, was more economic with his game and rarely had injuries compared to others. Worse the greats of the game often completely finished after 27. In football most players peak at that age, but in tennis Borg, Wilander, Hewitt, Roddick, Ferrero, Guga, Becker, Edberg, Safin, Mcenre etc were finished at the top level.