When children line up on the playground to have a kick-around, very few request to play the position of full-back.
It is, perhaps, the least glamorous role, and the one that often receives the least credit. But it can be one of the utmost importance to a team.
Manchester United have been blessed with many elite players to have fulfilled the role, the likes of Tony Dunne, Denis Irwin and Gary Neville immediately come to mind.
Here are the Red Devils' 10 best of all time.
Spell at Old Trafford: 1960-1967
First up we have Noel Cantwell—a key player in the post-Munich air disaster period for United.
The Irish full-back arrived at Old Trafford at the peak of his playing career, seeing out his days for Matt Busby's side.
Originally a cricketer, Cantwell unfortunately retired a year before the Red Devils' European Cup-winning campaign of 1967/68 but is best remembered for captaining the team that won the FA Cup in 1963.
Spell at Old Trafford: 1919-1934
You'd be hard-pressed to find a Manchester United fan who remembers watching Jack Silcock play for the side.
The Lancashire-born left-back was a mainstay of the post-WWI team, making an impressive 423 appearances during his loyal 15-year stint at the club.
The official club website describes the England-capped Silcock as a "strong, skillful full-back with excellent distribution skills."
Spell at Old Trafford: 1974-1988
A solid and reliable player at left-back, Arthur Albiston remained at Old Trafford for the best part of 15 years.
From the youth setup to the first team, the Scotsman wasn't the most adventurous player of his position in England, but he was rarely caught out of position on the defensive end as a result.
Albiston currently sits in 10th on the all-time appearance list for United players.
Spell at Old Trafford: 2006-
Next up is a name all fans of the Red Devils will recognise—United's current first-choice left-back, Patrice Evra.
At the peak of his career around 2008, the Frenchman was widely considered the best player in his position in world football, though his influence, particularly on the attacking front, has since diminished with age.
While at Old Trafford, Evra has won four Premier League titles, three League Cups and has one Champions League winner's medal to his name.
Spell at Old Trafford: 1958-1970
There are few United players who can compare in popularity to the English-born, Irish international right-back Shay Brennan.
Brennan made his debut for the club in the first game following the Munich disaster of 1958, scoring two goals to instantly cement his legend.
He was a strong, physical defender who possessed his fair share of skill too.
Brennan was the first member of the 1968 European cup-winning side to pass away. Over 1000 people attended a subsequent benefit match to celebrate his life and career.
Spell at Old Trafford: 1990-2002
Have Manchester United had a more reliable player in the last 20 years than Denis Irwin?
The left-back was a model of consistency, providing a marauding threat down the left flank, while also offering more-than-able defensive skills on the back foot.
While at United, Irwin won the Premier League a total of seven times, successfully adapting with every new team Sir Alex Ferguson put together between 1990 and 2002.
Spell at Old Trafford: 1951-1958
A right-footed left-back, Roger Byrne possessed unusually attacking instincts for a player of his position during the 1950s.
As captain of the Busby Babes and a regular in the England international team, Byrne was an inspirational leader for the young, prodigious side.
At the age of 28, he was one of the unfortunate souls who passed away in the Munich air disaster.
Spell at Old Trafford: 1960-1973
Signed for £5,000 in 1960, Tony Dunne quickly became a key player in Matt Busby's post-Munich side of the 1960s.
The pacy left-back was a creative threat for the Red Devils in attack, while also being a consistently reliable and committed presence in defence.
Released by United in 1973 aged 32, Dunne went on to make a further 200 total appearances for Bolton Wanderers before retiring—his passion for the game undying.
Spell at Old Trafford: 1992-2011
Though he was not the most talented defender of his generation, there were none more loyal and dedicated to the simple cause of winning than Gary Neville.
The right-back is best remembered for his telepathic partnership with close friend David Beckham down the wing, with the two linking up to cause opposition defenders nightmares.
Now both a pundit and coach, Neville remains a steadfast Manchester United supporter, though this rarely prevents him from offering unbiased opinions.
Spell at Old Trafford: 1937-1953
Manchester United's captain from 1946 to 1953, Johnny Carey was a key member of the successful post-war side under Matt Busby, winning the Footballer of the Year award in 1949.
He is widely regarded as one of Ireland's finest ever players and was the first player from his country to win a major trophy at Old Trafford.
According to his obituary, the gentlemanly Carey was known for his "scrupulous fairness and unruffled demeanour no matter how dire the circumstances" (via The Independent).
Will Rafael eventually make it onto this list? Exactly how good do you think the Brazilian could eventually become?