There is broad agreement Alexis Sanchez has not been the same player since he joined Manchester United.

Actually, this is slightly inaccurate. Sanchez has not been the same player for longer than that. The more I watch him in a Manchester United shirt, the more convinced I am his poor final year at Arsenal was not due to a declining team or loss of motivation as he prepared to leave.

Sanchez's best years have gone. He is to Manchester United what Fernando Torres was to Chelsea.

It happens. As footballers we enjoy peak periods and there is a common assumption this is usually between the ages of 27-32. With strikers that is not always the case. Some of the best I played with – Torres being a prime example – were never better than in their early to mid-20s.

Their appetite for goals and their matchwinning potential means when they burst onto the scene they not only want to play every match for club and country, but under-pressure managers cannot resist using them as much as possible. There is a clamour for them to play from fans and media, so they do not rest enough. After too many games they suffer an increasing number of injuries, burning themselves out earlier than defenders and midfielders.