Kai Havertz's rise from promising youngster to bona fide star and leader at Bayer Leverkusen was rapid. Now he departs for Chelsea and the English Premier League with valuable experience to go with his astronomical talent, especially since it's still early in his footballing journey.

The story for Havertz began in the village of Mariadorf, just north of Aachen. It's where the attacking midfielder both grew up and got early guidance in the sport.

"My grandpa really got me into football," Havertz told bundesliga.com. "He helped me take my first steps. Obviously, my brother and father also did their bit to get me out there playing at an early age. Everyone was football crazy, and we were just a football family. We loved football and everything revolved around it, so I grew up with it and that's how this passion developed."

Havertz joined his first club, Alemannia Mariadorf, aged just four. His grandfather, Richard, was the long-time chairman at the club and some say he passed on his own gift for the game.

"People were always saying I had the potential to make a career of it," Havertz said. "But then it’s still 10, 12 years to work to get the chance to play in the Bundesliga or any other top league."

After spending most of his time with Mariadorf in age groups two years above his own, in 2009 - aged 10 - he joined Alemannia Aachen – the biggest club in the region. At that time, they were a Bundesliga 2 side, and Kai was a regular fan.

Watch: Havertz's attacking masterclass unlocked

"The best time was when Erik Meijer was playing up front," Havertz explained. "Aachen had some fantastic players over the years - some of my own early heroes."

The youngster only lasted one year at Aachen, though. Not because he wasn't good enough, but because he had shown he was too good. Scouts had been watching Havertz play for several years, but a performance against Leverkusen made one talent spotter want a second look.

"Kai was playing for Alemannia Aachen's under-12s - he was a year younger than everyone else and playing against our [Leverkusen]'s under-12s," said Slawomir Czarniecki, a youth coach at the BayArena. "I don't remember exactly how the game finished - 8-3 for us I think - but he scored their three goals. That was my first impression of Kai."

Kai Havertz led his Bayer Leverkusen U17 side past Borussia Dortmund in the German final. - imago

Havertz joined Leverkusen in the summer 2010 and continued his progression through the ranks. Up to that point, the left-footed playmaker had overcome every obstacle in his path, but then his body made life hard.

"At 14 or 15, I was still one of the smallest players in the team," Havertz said. "Then I went through a pretty dramatic growth spurt. I had to get used to my legs being longer - it affects the whole way you play football. There was definitely a bit of a struggle, especially at U15/16 level. I wasn't starting as many games - spending more time on the bench."

Havertz, though, soon came through those teething problems to help Leverkusen win the German U17 title in 2016. The teenager scored 18 goals in 26 games - including the opener in the 2-0 win over Borussia Dortmund in the final - to lead his team to glory.

Nine months later, he would play for the first team against BVB at the Signal Iduna Park.

Watch: Havertz on the Bundesliga

That was one of 24 Bundesliga appearances Havertz made for Leverkusen in his debut season at senior level - as well as three in the UEFA Champions League - having become the club's youngest-ever debutant against Werder Bremen in October 2016. Four goals and six assists in the Bundesliga made a lasting impression on the league, and his teammates could see they were in the company of a rare talent.

"He's got great composure and technique, and his decision-making is usually spot on," said Leverkusen striker Kevin Volland. "I've seen him come right through into the first team since I joined the club and his development has been incredible. He's quickly become especially important to us."

While Havertz was making his first strides on the pitch, it was also a crucial time off it. The teenager was finishing secondary school around the time he broke into the Leverkusen first team, which led to some difficult challenges. Havertz explained one of those in particular when asked about the hardest moment of his career so far.

Tweet translation: 'A good finish is important - not just on the football field. Good luck Kai Havertz with your exams!'

"I had to do my secondary school exams at the same time as playing in the DFB Cup," Havertz explained. "I had an exam on Wednesday after an away game on the Tuesday evening that went to extra time and penalties. I got home relatively late and had to do an exam the next day. I don't want to talk about how the exam went!"

Havertz even missed a Champions League last-16 clash with Atletico Madrid to finish his exams, with Leverkusen giving him three days off during the week in order to complete his A-levels.

Havertz missed only four league games in his second season in the German top flight, scoring three goals and making nine more in the 2017/18 campaign. He soon made himself known to anyone who had not previously noticed his extraordinary talent in his third full campaign. At the age of just 19, the Germany international netted an eye-catching 17 league goals in 2018/19, starring in his team's late charge for a top-four finish.

Watch: All of Havertz's goals and assists in 2019/20

In doing so, he became the youngest player to reach 30 Bundesliga goals and the records continued to tumble in 2019/20. In December 2019 against Cologne, Havertz became the youngest player to make 100 Bundesliga appearances – at just 20 years, six months and four days old.

He showcased his flexibility too, impressing in a more central attacking role in the second half of the campaign to end with 12 league goals and as a DFB Cup runner-up. Along the way, in May 2020, Havertz fired Levekursen past Freiburg to become the first player in league history to reach 35 goals scored before turning 21.

The Germany international turned 21 a month later, and did so as a true leader for Leverkusen - having already worn the captain's armband and taken further responsibility as a penalty taker. In the blink of an eye, he's turned from an exciting young prospect to one of the best players in Europe.