On the face of it, the job of the ball boy - or ball girl, of course - may seem rather insignificant.
However, football wouldn’t be anywhere near as fast-paced a sport without them.
As soon as the ball goes out of play, it’s their job to give either the same ball or a different ball back to one of the players as quickly as possible.
On the whole, they do an excellent job. However, there have been a few memorable examples of biased ball boys failing to give the opposition the ball quick enough because the home team is winning or has some other sort of advantage.
Chelsea’s Eden Hazard was shown a straight red card for kicking Swansea City ball boy Charlie Morgan during a League Cup match in January 2013. Morgan fell on top of the ball and the frustrated Belgian, in an attempt to retrieve the ball, inadvertently hurt the lad.
But these incidents are extremely rare. Ball boys and girls operate in every match and, by and large, there are virtually no problems.
Certain clubs will use players from their youth academies as ball boys on match days.
And some of these players have gone on to become famous footballers themselves.
Let’s take a look at several photos showing ball boys who went on to become football stars in their own right years later, via Spanish newspaper Marca.
The Spanish teenager, who completed his move to Real Madrid from Manchester City at the weekend, can be seen here watching on as Isco and Santi Cazorla celebrate scoring a goal for Malaga.
Diaz, now 19, was a youth player at Malaga between 2010 and 2013.
He might be one of the most celebrated players in Real Madrid’s history, but Raul spent two years in the youth ranks of local rivals Atletico.
Here he is alongside former Atleti forward Manolo in the early 1990s.
Wesley Sneijder joined Ajax’s youth academy in 1991, when he was just seven years old.
The attacking midfielder, who went on to represent the Dutch national team 131 times, can be seen here alongside the great Frank Rijkaard.
A Boca Juniors man through and through, Carlos Tevez poses alongside a very youthful-looking Juan Roman Riquelme at some point during the late 1990s or early 2000s.
Tevez made his professional debut with Boca in 2001 before leaving the Bombonera in 2004. He briefly returned in 2015 and then came back for a third spell last year.
If Steven Gerrard knew the young lad next to him would go on to play for Real Madrid, he might have actually acknowledged him.
Kovacic, who is currently on loan at Chelsea, tried to get Gerrard’s attention after a Champions League match but didn’t appear to have much luck.
Iago Aspas watches his beloved Celta Vigo in action against AS Roma.
The striker, who endured a disappointing spell with Liverpool a few years back, is now 31 years old and a Celta legend.
A wonderkid during the early 2000s - Championship Manager fans will remember him well - Andres D'Alessandro is seen here alongside Enzo Francescoli while at River Plate.
Fun fact: Zinedine Zidane named his first son after Francescoli, who was a wonderful footballer.
Arda Turan, one of the most talented Turkish players of modern times, was photographed back in the early 2000s celebrating a Galatasaray goal with a ball in his hands.
Now 31, Arda is currently on loan at Istanbul Basaksehir from Barcelona.
Like Raul, Alvaro Morata started out in Atletico’s youth ranks before joining Real Madrid.
The Spanish striker, who is currently with Chelsea, can be seen here alongside some of his pals at the time.
A football fanatic from the start, Pep Guardiola was both a fiercely passionate Barcelona fan and ball boy for the Catalan giants during his youth.
Here he is behind Victor Munoz as Barça celebrated a title…
And here he is again behind Terry Venables, who coached Barça during the mid-1980s…