There has been a plethora of young talent bursting onto the football scene in recent years.
One such player, Kylian Mbappe, announced his arrival in the 2016-17 season. He scored 15 Ligue 1 goals and six Champions League goals for Monaco to catch the attention of PSG.
The French giants soon snapped up the then-teenager, who went on to register 132 goals and 61 assists across all competitions to win a plethora of titles with the club. He has also shone on the international stage, becoming the first teenager since Pele (1958) to score in the FIFA World Cup final.
Similarly, other young players like Jeremy Doku and Ryan Gravenberch, to name a few, have also produced impressive performances for club and country despite their tender years.
On that note, let's take a look at the five most valuable 21-year-old players in the game at the moment:
#5 Matthijs de Ligt - €75 million
Matthijs de Ligt is widely regarded as one of the best young defenders in the game at the moment.
The young centre-back led from the front as Ajax made a fairy-tale run to the Champions League semi-finals in 2018-19 to catch the attention of Europe's top clubs. Juventus won the race for his signature, snapping up the then-teenager for €75 million.
Strong in the air, good on the ball and possessing keen positional awareness, De Ligt took his time to get going in his new surroundings. However, he soon became a key player in the first team and has won a Serie A and Copa Italia title in his two seasons in Italy.
De Ligt, who is also a mainstay in the Netherlands team, is the subject of interest from many top clubs across the continent. However, he is expected to stay at Juventus and continue his development.
#4 Phil Foden - €80 million
Since debuting in the Premier League in 2017, Phil Foden has improved by leaps and bounds under Manchester City's legendary manager Pep Guardiola.
Foden, a three-time Premier League winner, has registered 15 goals and eight assists in 69 games in the competition. The 21-year-old enjoyed a career-best nine-goal, five-assist season in Manchester City's triumphant league campaign last season.
Phil Foden, who also scored thrice and assisted as many in Manchester City's run to their maiden Champions League final, has received high praise from Guardiola. The Spanish tactician has called Foden the most talented player he has ever seen, saying:
"He (Phil Foden) is the most talented player I have ever seen. The best is Messi, first. (But), I didn't meet Leo Messi at 17 when I met Phil (Foden), and (at) that age, I've never seen a player with (Foden's) potential. But you have to see it on the pitch and on the biggest stages."
#3 Joao Felix - €80 million
Joao Felix is one of the most exciting young attackers in the game. Nevertheless, eyebrows were raised when Atletico Madrid splurged a whopping €127 million for the then-teenager's services in the summer of 2019.
Following a breakout season at Benfica, the 21-year-old has largely failed to replicate the same exploits at Atletico. He has scored just 19 times in 76 games across all competitions.
The young attacker, who remains a work in progress, made a promising start to his 2020-21 campaign for the eventual champions but faded as the season progressed.
Felix is also yet to make his mark for Portugal, scoring just thrice in 18 appearances. The 21-year-old, who plays as a second striker, played just one game at Euro 2020 as holders Portugal crashed out of the competition in the Round of 16.
#2 Jadon Sancho - €100 million
Manchester United finally succeeded in their year-long pursuit of Jadon Sancho, as they managed to land the English winger on an €85 million transfer this summer.
Only 21, Sancho has had a successful four-season stint at Borussia Dortmund, scoring 50 goals and assisting 64 times across competitions.
In fact, Sancho's tally of 41 league assists in the last three seasons is only exceeded by two other players in Europe's top five leagues.
Although he made news for all the wrong reasons - he was one of three England players who missed their spot-kicks in the team's penalty-shootout defeat to Italy in the Euro 2020 final - Sancho is expected to hit the ground running at Old Trafford.
It remains to be seen if the 21-year-old lives up to the pressure of his lofty price tag and produces befitting performances.
#1 Erling Haaland - €130 million
Erling Haaland is one of the most prolific goalscorers in the game at the moment, usurping the likes of Cristiano Ronaldo and Lionel Messi. He made a sizzling start to life in the Champions League, becoming one of the youngest players to score a hat-trick on his competition debut.
The young Norwegian has gone from strength to strength since then. He has continued to score goals galore since moving to Borussia Dortmund last year and is now the subject of interest from a plethora of top clubs across the continent.
Haaland has scored an impressive 60 times in as many games for the Bundesliga giants, with 41 of these strikes coming last season.
Considering the interest in his services, Haaland is unlikely to remain at Dortmund for too long. Nevertheless, the 21-year-old has opened his 2021-22 campaign with a hat-trick in the DFB Pokal as he looks set for another goal-filled season.