Ever wondered why Bayern Munich goal machine Robert Lewandowski wears No.9 and not No.3, or why Borussia Dortmund attacking midfielder Marco Reus dons double instead of single digits? bundesliga.com plays the jersey numbers game…

Introduced to the German game at the start of the 1948/49 season, soccer jersey numbers were originally created to identify certain positions in a tactical formation at a time when player names were not used on the back of shirts.

As there were 11 players on the field, numbers went from 1 to 11, with substitutes starting at No.12, and players assigned the jersey number that tallied with their position. It really was that simple.

Traditionally, numbers and roles in German soccer corresponded in the following fashion:

#1 - Goalkeeper

#2 - Right-sided defender

#3 - Left-sided defender

#4 - Central defender

#5 - Central defender/ Sweeper

#6 - Defensive (deep-lying) midfielder

#7 - Right-sided midfielder

#8 - Central midfielder

#9 - Centre forward

#10 - Second striker

#11 - Left-sided midfielder

#12+ - Substitutes

Over time, numbers became associated with certain roles and players. The No.5 jersey, for example, is synonymous in German football with 1970s icon Franz Beckenbauer - the archetypal sweeper and one of the world’s all-time greats. German sportswear giant adidas still produce runs of No.5 Beckenbauer shirts to this very day.

Franz Beckenbauer's (2nd.l.) No.5 jersey might just be the most famous in German football. - imago sportfotodienst

Number-role associations remain strong, even if evolving formations and positions have triggered a noticeable break with convention.

Until 1994/95, Bundesliga jersey numbers were assigned on a match-by-match basis to the players who took to the pitch on the day. No player had a claim to a particular number unless he played in the position corresponding to that number, so a right-back could not choose No.9, only No.2.

Since 2011/12, German Football League regulations have permitted Bundesliga clubs to assign members of their squad ANY number from 1 through 40 at the beginning of a season, with only No.1 reserved for a goalkeeper - first-choice or other.

Manuel Neuer is Bayern Munich and Germany's No.1 in more ways than one. - 2019 Getty Images

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The loosening of the rules means players can indulge their own superstitions by requesting, for example, a lucky number or birth date - as long as it doesn’t exceed 40.

A comparison of Bayern’s 1995/96 average starting line-up with their 2018/19 Bundesliga-winning equivalent highlights the shifting trends:

Bayern, 1995/96

#1 - Goalkeeper (Oliver Kahn)

#2 - Right-sided wing-back (Markus Babbel)

#5 - Central defender (Thomas Helmer)

#6 - Defensive midfielder (Christian Nerlinger)

#7 - Attacking midfielder (Mehmet Scholl)

#8 - Central midfielder (Thomas Strunz)

#10 - Sweeper (Lothar Matthäus)

#14 - Attacking midfielder (Ciriaco Sforza)

#17 - Left-sided wing-back (Christian Ziege)

#18 - Striker (Jürgen Klinsmann)

#21 - Striker (Alexander Zickler)

Highest first-team squad number - 23

"Nine plus nine equals 18, right?" Jürgen Klinsmann wore No.9 at VfB Stuttgart and No.18 at Bayern. - imago/Fred Joch

Bayern, 2018/19

#1- Goalkeeper (Manuel Neuer)

#4 - Central defender (Niklas Süle)

#5 - Central defender (Mats Hummels)

#6 - Deep-lying midfielder (Thiago)

#8 - Defensive midfielder (Javi Martinez)

#9 - Lone striker (Lewandowski)

#22 - Right winger (Serge Gnabry)

#25 - Second striker (Thomas Müller)

#27 - Left-back (David Alaba)

#29 - Left winger (Kingsley Coman)

#32 - Right-back (Joshua Kimmich)

Highest first-team squad number - 39

Watch: Joshua Kimmich, the best No.32 in the business

In their most basic terms, jersey numbers are functional, helping to identify players, and - to a lesser extent - positions.

Some clubs have even retired the shirt numbers of legendary players (Lukas Podolski’s No.10 at Cologne). Bayern and Werder Bremen have gone one step further by withdrawing No.12 in honour of the fabled 12th man - the fans.

There are cultural variations, too. The Dutch traditionally allocate No.5 to left-backs; the Italians assign No.4 to the German No.6 and vice versa; and there will always be the odd eccentricity.

Born in 1969, standing at 1.69m tall, and tipping the scales at 69 kilos, Bixente Lizarazu got away with No.69 at Bayern in the Bundesliga’s pre-1-40-or-bust years.

The No.77 emblazoned the shirt of Andreas Görlitz in 2007/08 at promoted Karlsruher in a nod to his rock band, Room 77; while dyed-in-the-wool centre forward Sandro Wagner’s second bite of the cherry at boyhood club Bayern was reflected in his choice of the vacant No.2 shirt.

"Could I have that for my collection?" Oliver Kahn's (r.) former Bayern teammate Andreas Görlitz (l.) turned heads with his choice of jersey number at Karlsruher. - imago sportfotodienst

It might not be what traditionalists want to see, but a right-back does not have to wear No.2 to operate as a right-sided defender. Just ask Bayern No.32 Kimmich, or his World Cup-winning predecessor, Philipp Lahm - another paragon in the position and German soccer’s most famous No.21.

The days of starting line-ups made up exclusively of numbers 1-11, corresponding rigidly to positions, are a thing of the past.

Click here for our Bundesliga soccer positions explainer!