Yes, social media and video games really can hurt footballers' decision-making | Sean Ingle

Study of footballers in Brazil shows spending time on a smartphone or console before a game causes mental fatigue

Could spending too much time on Twitter, Facebook or Instagram affect a footballer's performance? Manchester United appear to think so. One report before their trip to Anfield claimed the club were "consulting leading experts" about how to help their stars deal with the negative mental effects of social media and also suggested there were concerns that players were suffering dips in form as a result of being abused online.

Some may suggest the players should just "man up". But scientists are increasingly scrutinising how mental fatigue - the lack of energy we feel from long periods of purely cognitive activity - can influence sporting performance, often with startling results.