The position of a full-back is one that has evolved over the past few decades with changes in formations, positioning and tactics all contributing to the centre-backs being pushed further back and the full-backs going wider and more forward.
They are primarily used in a formation that has four defenders at the back with the two full-backs flanking the two centre-backs in the middle.
Thus, the natural preference is to deploy a left-footed player for the left and a right-footed player on the right side.
Some of the biggest names in world football have specialized and dominated these positions for years and the skillset required includes great strength, pace, excellent game-reading and man-marking in order to prevent attacks and the ability to deal with tricky wingers.
This role requires incredible stamina for running up and down the wings to put in crosses for their forwards to score and to track back equally fast if the ball is lost to the opposition.
Wing-backs are used in a formation that uses three central defenders at the back. The wing-back is a position that is preferred in a 3-5-2 formation as an attacking option or in a 5-3-2 formation.
With teams opting to play attacking football and exploit the weakness of their opponents, the full-backs are usually crucial to the overall strength of every team.
This list includes five players who have stood out with their recent performances at club and national levels and are expected to contribute greatly to their national teams at World Cup.
#5 Nélson Semedo (Portugal)
Semedo is an offensive full-back with superb physical attributes who was a key player in Benfica’s title-winning campaign in Portugal. He moved to Barcelona in 2017 from Benfica for €30.5 million.
Having played a stellar season for the Águias (Eagles), the Portuguese has ably filled the right-back gap left at Barca following Dani Alves's summer 2016 departure.
Blessed with pace, power and an eye for a killer pass, the right-back has progressed quickly to the highest level, both with his club and the Portuguese national side.
Semedo has the attitude and technique to be world class; the pace, and vision to be able to float in crosses and create chances for the team.
His ability to dribble allows him to dominate the right flank, track-back quickly if his team loses possession, mark his man throughout the game and a simplicity to his game that seems to make even the cheekiest of skills look natural.
His connection with other players on the field is spectacular and he is also a loved figure in the dressing room (ignoring the spat he had with Neymar at the start of the season).
With injury hindering his progress in the later stages of the domestic season, the 25-year-old looks set to return to full match fitness in time to help Barca make a final assault in Spain and Europe.
Semedo’s ability to tear up-and-down the flank with the dribbling speed and skill of a top European winger will give Portugal an all-new dimension to their deadly attack spear-headed by none other than Ronaldo.
As the reigning European champions, the World-Cup will be important to the Seleção das Quinas and the right back; after all, it is not every day that a player gets to play with Cristiano Ronaldo and Leo Messi in their career.
#4 Thomas Meunier (Belgium)
The World-Cup just wouldn't come any earlier for Thomas Meunier. Signed by PSG for €7m from Club Brugge on a four-year deal in 2016, the Belgian right-back has had a mixed career so far.
Having competed with Serge Aurier throughout his first season, he often appeared on the substitute bench, due to good performances by Aurier.
This season though, 26-year-old has settled in the French capital and has had a good season so far. In a team led by one of the deadliest attacks in Europe, the defence is not a major concern, but Meunier and company seem to be doing a good job.
This season, he has made 16 appearances in Ligue 1 and has also featured in the Champions League once, which is impressive; given the fact that his direct competition for a starting-XI spot is none other than Dani Alves.
Possessing great man-marking skills, physical strength, the ability to intercept attacks, and pace to run down the flanks to running up and down the right-wing to put in crosses for his forwards, Meunier plays a considerable role at both ends of the pitch.
The Belgian has a knack for attacking, having scored five and assisted five in 25 games this season, an impressive stat for a full-back.
With his position in the national squad all but cemented, the player interested in a transfer away from the French giants in the near future and clubs across Europe interested, the World-Cup is going to be a crucial stage for the player.
#3 Djibril Sidibé (France)
Sidibé had to be on this list. The French International has had a stellar season in Ligue 1 so far and although many of his teammates have left the club for greener pastures, the full-back has continued his diligent work for AS Monaco and is generating attention across Europe.
With some big clubs reportedly interested in his signature, it makes the World-Cup an all-important campaign for the right-back.
Sidibe, who moved from Lille in 2016; has had a wonderful spell this season with three goals and eight assists in 29 games for his team.
With a French squad that has some great talent, securing a starting-XI spot in the national team is tough, but Sidibe seems to have cemented his position.
France's attacking and counter-attacking game is often wing-oriented, with plenty of emphasis on the full-backs, making the role pivotal.
Sidibé has incredible technical skills and he is quick enough to track a player and also go ahead and put a fine cross either on the overlap or by carrying the ball out of his defensive half on his own.
An additional benefit of the France international’s game is his ability to alternate between the right and left flank.
Sidibé has frequently featured in the left-back position for Monaco, playing well enough to suggest that, while it may not be his natural side, he is more than able to fill this role, a key factor for his selection in the starting line-up.
His technical, tactical and athletic capacity have often been integral to his side’s overall strategy in most matches as his energy allows him to patrol the touchline and make overlapping runs and crosses, which will be needed in plenty, to feed the attack that the French National team boasts.
With a major part of his five-year deal still ongoing, a summer transfer may or may not be a priority for the Monaco man, but to play at the ultimate level is every player's dream.
#2 Dani Alves (Brazil)
Dani Alves is a gift that keeps on giving, so enjoy him while you can. Regarded as one of the best full-backs of his generation having played for Sevilla, Barcelona, Juventus and PSG.
Alves is an offensive right-back or wing-back well-known for his pace, stamina, overlapping attacking runs, technical skills and also for inspiring a generation of youngsters across the world. The Brazilian has won everything for club and country but the World-Cup.
Alves is right in the middle of an incredible career renaissance at PSG after he looked a spent force at the start of 2015.
Alves is a unique genius of a player, a galloping full-back and a studious central midfielder, who thrives so much in the big games that even at his age, you’d never bet against him.
He offers his teams an unparalleled amount of assistance in match control, and then he is also an accurate striker of the ball and is known for his ability to score goals in particular from outside the area or through set-pieces.
By the time the World-Cup starts he will be 35 and comfortably the oldest man on this list but the experienced Brazilian star has now won 36 trophies in his professional career which appears to have made him the most decorated footballer in the world.
Alves has also won three trophies with Brazil, winning the 2007 Copa America as well as the Confederations Cup in 2009 and 2013.
A regular on the FIFA FIFPro World XI, UEFA Team of the Year and many other polls, Alves deserves the spot on this list not for the future that the World-Cup might hold for him, but to enjoy the phenomenon that Alves is on the big stage for one last time.
If Brazil are to mount a serious challenge, they should do it as a testament for the contribution to the game by a player so noble of heart, he was willing to donate a part of his liver for his friend's treatment for liver cancer.
#1 Joshua Kimmich (Germany)
One of the brightest young talents in German football, Joshua Kimmich, once deemed not strong enough to play professional football by his coaches, is already a cornerstone for both his club and country.
The German moved to Bayern Munich from Stuttgart for a reported fee of €7 million in 2015 and has played 109 matches for Bayern in all competitions, scoring 13 goals, winning five trophies in the process.
His hard work was recently awarded by a contract with a three-year extension with Bayern Munich.
His rise to the top has been phenomenal, having established himself as Phillip Lahm's successor in both the German national team and the Bayern Munich Squad.
Originally a central midfielder he now plays as a right back but can also play as a right midfielder and as a makeshift centre-back.
A product of RB Leipzig, Kimmich was part of an extremely attack-minded team in which his ball-winning qualities in front of a high back four shone through and his smart positioning and reading of plays helped him shut down faster players on defense.
On the attack, Kimmich combines his vision and stealthy positioning with his quick feet and thinking, regularly getting into the right positions to score, create chances or initiate counter-attacks.
With the Bavarians on track for a sixth successive Bundesliga title, and in the Champions League race, Kimmich has had a fruitful domestic season so far, with his admirers hoping for him to carry his form to the World Cup.
Kimmich appears to be a crucial member for Bayern and Germany for years to come and with a gameplay that boasts a Lahm-Thomas Müller hybrid, a concoction of traditional German toughness and modern tactical flexibility, he could even be a future captain of club, country or both.