A scrambled last-minute set-piece goal. A controversial penalty. A high-profile mistake. An inspirational individual or team performance. A lucky day. A greater desire to succeed.
Football is often referred to as "the greatest game on Earth" because it is always unpredictable and never dull.
For example, Spain were one-to-four favourites to beat Switzerland in their opening Group H match at last summer's FIFA World Cup. They lost 1-0 and, as a result of their shock defeat, their odds of winning the tournament for the first time ever lengthened considerably—from three-to-one to five-to-one. Inevitably, they would go on to win the tournament.
Another example of why it is so dangerous to bet money on football came at the start of this season in the Premier League. Wigan Athletic's first three-league fixtures read: Wigan 0-4 Blackpool, Wigan 0-6 Chelsea, Tottenham 0-1 Wigan. Anyone who knows their Bale from their Berbatov will realise that on any given Sunday, the Latics are not one goal better than Spurs and they are certainly not four goals worse than newly-promoted Blackpool!
So in the following video and photo slideshow, I take you through the 50 most shocking upsets in the history of world domestic and international football. I am sure I have missed many cases so please feel free to add your contributions.
Enjoy the freak show!