Little was known about Jadon Sancho when he sealed a move to Germany in August 2017. As he gets set for a reunion with his former club Manchester City in the UEFA Champions League quarter-finals, it's clear now that Borussia Dortmund got one of the steals of the century when they signed the England winger.

Sancho's next Bundesliga game will mark his 100th appearance in the German top flight. With 36 goals and 43 assists in his first 99 games, he has certainly left his mark.

Despite his natural talent, though, there was no guarantee that he would. Sancho took the No. 7 jersey freed up by Ousmane Dembele's departure for Barcelona, and - still only 17 at the time - he was sent on for his debut in a 2-2 draw with Eintracht Frankfurt in October 2017.

A fresh-faced Sancho made his Bundesliga debut on Matchday 9 against Eintracht Frankfurt in October 2017. - imago

"I was so nervous," Sancho told FourFourTwo magazine of his "dream come true" moment. "Scared even. Dembele had just left and the fans were thinking 'Who's this No.7? He must be a big thing.'

"I'll never forget my first dribble. I tried to take on their full-back, he tackled me and I dropped to the floor. I couldn't get back up. Welcome to adult football, eh? I thought I had so much time and could do my own thing, then BANG! I knew I had to release the ball quicker after that."

As many a Bundesliga defender can attest, it wasn't long before Sancho began dropping them to the turf instead. His close control, quick feints and sharp movement made him a firm fans' favourite. While the Londoner admitted getting "goosebumps" playing in front of the famous Yellow Wall of Dortmund supporters, though, he has regularly helped energise that crowd with his vast array of skills.

His goals have, too, with the first of them coming from a cool side-footed finish in a 4-0 home win over Bayer Leverkusen in April 2018. As he often would, Sancho added a couple of assists for good measure in a victory that all but ensured that Dortmund would be playing Champions League football the following season. At 18 years and 27 days, the 2017 FIFA U17 World Cup winner was then the youngest English player to score in the Bundesliga.

Watch: Sancho's first Bundesliga goals

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"The way he controlled the ball to set up the third goal - that shows everything," Dortmund skipper Marco Reus said after Sancho's eye-catching performance against Leverkusen. "I wasn't that advanced at his age. So much respect!"

Sancho was looking more and more at home in a Dortmund shirt as he finished with 12 league appearances in his maiden 2017/18 campaign.

The rapid rate at which the youngster was developing continued in the following season, meaning he was a danger whether he started or not. After Sancho added a goal from the bench in a 7-0 win over Nuremberg in September 2018, Reus - who had a particularly good understanding with him on the pitch - felt the need to highlight his impact again.

"When our opponents ease off a little and Jadon comes into the game, then he's a weapon for us every single time," the Germany international said.

Sancho has been learning his trade from the best at Dortmund, and captain Marco Reus (r.) is a big fan of the youngster. - imagoimages

Sancho, though, was rarely left out of the starting XI in that 2018/19 campaign, playing an integral role in BVB's thrilling title challenge under Lucien Favre. He got his first brace against Hertha Berlin that October, then became even more popular with the Dortmund support by getting a derby winner at Schalke two months later.

Home and away against Borussia Mönchengladbach, in another win over Leverkusen, with another double against Mainz, and in a 4-0 Champions League crushing of Atletico Madrid: Sancho was scoring at regular intervals and in big games.

It was little wonder that in October 2018, Dortmund had given a new contract to a player that sporting director Michael Zorc billed as "one of the most exciting" in Europe.

"Everything I was hoping for has come true," Sancho said after he had put pen to paper on an improved deal. "This city loves football like no other, and at BVB young players get regular playing time."

Another dream would come to fruition just a few days later, since the form Sancho had been showing made him impossible for England boss Gareth Southgate to ignore. Sure enough, he was handed his England debut at the age of 18 with a substitute appearance against Croatia.

"I would say I'm a bit tricky, direct and just confident," Sancho said ahead of his first appearance for his country. "I believe in myself in one-v-one situations. I used to look at Ronaldinho, growing up, on YouTube. I just liked how he used to carry his team sometimes… and obviously, he used to try things that no one else would try."

It's easy to see that Sancho took inspiration from the former Barcelona and Brazil great, and his skills are a huge asset to Dortmund. Although his side would come up two points short of Bayern Munich in the 2018/19 title race, the English wide man was one of the reasons the 1997 European champions had come within touching distance of the Meisterschale. Sancho finished his second year in Germany with 12 Bundesliga goals and a league-high 19 assists.

Sancho has celebrated either scoring or providing an assist every 84 minutes on average across his first 99 Bundesliga games. - INA FASSBENDER/AFP via Getty Images

Averaging 35 sprints per game in his Bundesliga career, Sancho has the pace and the dribbling ability to hurt any team. He continued to make stunning progress in the 2019/20 season, so sometimes we needed a reminder that he would still experience peaks and dips like any other young player.

Then Dortmund boss Favre offered one in December 2019, after Sancho had fired his team into the Champions League round of 16 again with a goal and an assist against Slavia Prague.

"Jadon's a world-class player, no question about that," Favre told SportBild. "But you have to remember he's only 19 years old. It's hard to be outstanding in every game."

Watch: Dortmund's dream duo - Sancho and Erling Haaland

Sancho did his best to do just that, however, in a memorable 2019/20 season. His side finished runners-up to Bayern again, and the former Watford academy player once again broke his own personal records.

In what was just his third year as a first-team pro, he ended with a frankly absurd 17 goals and 16 assists from 32 league appearances. No Dortmund player has ever been directly involved in so many goals in a single season since detailed data collection began in 1992.

In light of such an extraordinary achievement, Dortmund's sluggish start to the 2020/21 campaign was brought into sharper focus, with neither the team nor Sancho able to consistently tap into their full potential. By the end of 2020 Dortmund were down in fifth place, Favre had been replaced by Edin Terzic as interim head coach, and Sancho had managed just three assists - and no goals - in 13 outings.

The new year brought a new BVB, however, and Sancho's upturn in form led to the side picking up more points. He has scored six and set up another six across 10 Bundesliga appearances in 2021, making him the first player under the age of 21 - he turned 21 on 25 March - to ever score 36 goals in league history.

Not only that, but he is averaging a goal or an assist every 84 minutes in the Bundesliga - another scarcely believable fact considering 79 of his 99 games have been starts.

"He's been working a little bit differently in training over the last few weeks and months, both in the gym and on the pitch," said teammate Mats Hummels when asked about Sancho's resurgence.

Dortmund's No.7 has indeed bulked up a little, and has even documented pre-training early morning runs at 5am on his Instagram story in recent months.

Watch: Sancho named February Player of the Month

"You get rewarded when you do that," Hummels continued. "That's something that attacking players sometimes need to learn, that hard work always pays off. He's been playing brilliantly and is one of the players who leads the way. We all know he's got attacking potential that few others have."

So now, with his century of senior club games on the horizon, Sancho's combination of speed, technique, killer instinct, experience and increasing physical strength could well haunt his former club on the continental stage.

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