In the modern version of the game, the role of a fullback is not just constrained to being defensive but the player has the additional responsibility of being part of the build-up play more and more.
Fullbacks are now expected to provide width to a team's attack while making overlapping runs and providing incisive crosses into the box.
Manchester City's recent spending on fullbacks like Kyle Walker, Benjamin Mendy and Danilo is evidence to the fact that the role of a fullback is gaining importance at every team now.
The beautiful game is evolving and the players have to keep up with it. On that note, we look at the top 5 left-backs in Europe right now.
#5 David Alaba (FC Bayern Munich)
The Austrian wonderkid has been lighting up the Bundesliga ever since his debut in the 2009/10 season for German giants Bayern Munich.
The 25-year-old was not as important to Carlo Ancelotti's system as he was for Pep Guardiola. Guardiola is someone whose tactics are based mostly on how the fullback operates in the wide areas.
Pep was the one who groomed Alaba to be a world beater at a very young age, but injuries have not helped his case. However, this does not create a moment of doubt about the talent that this guy possesses.
He can run up and down the flank with the ball at his feet while also combining with his teammates in congested positions making him perfect for the possession-based gameplay.
He has scored 3 goals and provided 4 assists for the German outfit in 35 appearances this year.
Injuries again have caused his season under Jupp Heynckes to be patchy but he has surely shown improvements over the last few months.
#4 Alex Sandro (Juventus)
The 27-year-old plying his trade in Turin is the archetypal modern full-back. He is quick, agile and has that technical ability a manager looks for in a modern day full back.
The former Porto player has 4 goals and 5 assists for the Bianconeri. The numbers don't fully represent what Sandro does for Juventus week in-week out.
His performances are such that the great Roberto Carlos himself called Alex Sandro his successor. This just goes on to show why Sandro was heavily linked to Chelsea for the whole of last year, but he ended up staying at Juventus.
Sandro might just leave when the transfer window opens again with Manchester United and a host of other European heavyweights also interested in signing up the Brazillian.
#3 Marcos Alonso (Chelsea)
The former Sunderland and Bolton player had to deal with a lot of criticism when his transfer to Chelsea was announced in summer of 2016. He has never looked back since.
His performances for Antonio Conte's side have been terrific to say the least. The former Fiorentina man has scored 7 goals and provided 3 assists for the London outfit this season. He also has an eye for the occasional freekick goal.
His style suits the formation that Antonio Conte likes to play with as he gallops down the left flank and joins in attack while also completing his defensive duties as a wing back in Conte's version of the 3-4-3.
His marauding runs down the left have also enabled Eden Hazard to drift inwards and inflict damage where he can best do it from.
#2 Jordi Alba (FC Barcelona)
Lionel Messi used to share an absolute telepathic understanding with Dani Alves on the right flank. Now that Alves has left Barcelona, Messi shares that same kind of fruitful relationship with Jordi Alba.
Alba was signed in the summer of 2012 from Valencia to replace an ageing Eric Abidal. Alba has carried on the good work done by the Frenchman in all those years.
He was constrained to the bench for most of the 16/17 season under Luis Enrique after the manager switched to a 3 man defence. Now, after the arrival of Ernesto Valverde and the departure of Neymar to PSG, Alba has found a new lease at life in the Catalan capital with more space on the left to make his bombarding runs on.
He has scored 3 goals and provided 8 assists in all competitions so far this term. Alba's pace has helped with his transition from defence to attack and vice versa. His pace has often led him to be the last defender when the Blaugrana are attacking set pieces.
#1 Marcelo (Real Madrid)
The Brazilian international has been the best left-back in the world for a while now. The 29-year-old was one of Real Madrid's standout performers as they won La Liga and the Champions League last season.
He was previously criticized for his lack of defensive ability when he joined the capital side but he has worked hard to improve and evolve his game. He has featured 4 times in the FIFA FIFPro World 11 in 2012, 2015, 2016, and 2017
Instead of providing overlapping runs to give width to the attack, he drifts inwards and creates danger from there. He has the technical ability that can be associated with most number 10's.
He has scored 4 goals and provided 6 assists for Los Blancos this season and is instrumental for Madrid's campaign in the Champions League.