You've undoubtedly heard it a million times now but the newest facet of modern football punditry rings true: Full backs are the most important positions on a football pitch. Of course, you need someone to stick the ball in the back of the opposition's net but the way teams are set up in today's football means, more often than not, managers try to find players to supply before they acquire a deadly finisher. If you have a Diego Costa in your team, you need at least three men to set him up. A midfield magician that plays intricate through balls, The Blues' Cesc Fabregas, and two flying full backs that provide width, pace and plentiful crosses for the big man to attack. Chelsea have that in abundance in César Azpilicueta and Filipe Luís, which is a big reason behind Costa being the joint top scorer in the Premier League as we speak with 14 goals. The shift in the modern day game means having majestical full backs is a must. Whether teams are playing a high pressing 4-2-3-1 or Louis van Gaal's 3-5-2, the full backs will still be expected to get up and down the field to fulfil their responsibilities of not only providers, but sound defenders too. Here are 20 left backs that are the missing piece to millions of tactical jigsaws around the parallel universe that is Football Manager 2015.