When Borussia Dortmund lined-up to face Manchester City in the first leg of their Champions League quarter-final, they knew they were going to have to make do without the injured Jadon Sancho.
Who interim manager Edin Terzic chose to replace the England international, though, came as a huge shock.
Despite having just 44 minutes' worth of first-team experience under his belt, teenager Ansgar Knauff was entrusted to start at the Etihad Stadium in what was Dortmund's first appearance at that stage of the tournament since 2017.
"I was in a good flow during that phase of the season," Knauff recalls when speaking exclusively to Goal and SPOX. "I had played my first minutes in the Bundesliga, assisted a goal against Koln after coming on and also felt good in training.
"Then, Jadon Sancho injured himself and the door opened for me. Suddenly being in the starting XI in that game is something I will never forget in my life.
"Edin previously took me aside in training and explained a lot of tactical things to me. After a video meeting, he showed me again exactly where the space could be for me to run into. In the end, he chose me because against such a high- pressing team like Man City, we could counterattack using my pace and ideally create scoring chances.
"Of course, I was really looking forward to the whole experience, but I also tried to suppress my nervousness. In such a situation, however, you can probably never turn it off completely. When the game was on, I was fully involved and didn't think about it much anymore.
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"What impressed me the most was how extremely strong City are as a team. Kevin De Bruyne and Ilkay Gundogan's ball retention was also incredible. The passes they choose to play with ease in the midfield is really outstanding.
"Still, we did really well against them and only narrowly lost both games. With a little more luck, we really could have done more."
Spurred on by the confidence shown in him, Knauff backed up that performance by netting the winner against Stuttgart four days later, cementing him as yet another youngster to watch out for at Signal-Iduna Park.
If Ansgar Knauff's first #Bundesliga goal is anything to go by, @BlackYellow fans have got a VERY exciting few years ahead! 🙇♂️🥶 pic.twitter.com/tow51i88OP
— Bundesliga English (@Bundesliga_EN) April 15, 2021
Dortmund, of course, have built a reputation as being the ultimate finishing school for the world's best teenage talents, with the likes of Sancho, Erling Haaland and Jude Bellingham choosing the Bundesliga outfit to showcase themselves to the world before likely joining one of Europe's richest teams in the not too distant future.
The club, though, is still producing players of its own too, and while Youssoufa Moukoko is the current standard-bearer for the BVB academy, Knauff is another who owes much of his footballing education to the Black and Yellows.
The 19-year-old joined Dortmund in 2016 from Hannover, though he had already had a brush with the club two years previously when playing for his first junior team, SVG Gottingen.
Having been named Player of the Tournament at the Opel Family Cup, the then-U12 was presented with his trophy by Jurgen Klopp, with a photograph of the pair having gone viral this year after Knauff's memorable week in early April.
"We qualified for the final tournament in Dortmund over four rounds played across Germany," Knauff explains. "That was a huge success for our team.
"The trips there or the overnight stays in the hotels were great experiences. We were then at a BVB game in the stadium.
"He (Klopp) was there most of the time – he was like the face of the tournament. When he handed me the trophy, he told me that I played well and congratulated me.
"Part of my award was that I got a pair of football boots and my mother and I were invited to Dortmund for two days. Then I trained with the Under-13s, and we went to a game in the stadium again.
"At that time, however, there was no prospect of moving to BVB one day. That was still far too far away."
Knauff eventually moved to Dortmund at the age of 15, where he lived in the boarding rooms alongside a number of the other young prospects.
He impressed almost immediately, and by the time he had reached the U17s he was a key player, scoring four goals and laying on 10 assists across the course of the 2018-19 campaign.
That included direct contributions to five of Dortmund's six goals in their play-off semi-final win, as well as a goal in the final against Koln; an event which allowed sporting director Michael Zorc to watch him live for the first time.
A year later, Zorc oversaw Knauff's promotion to the first-team squad for pre-season training after a 2019-20 campaign in which he scored seven goals, including both in a 2-1 win over Inter in the UEFA Youth League, and laid on seven assists for the U19s.
"Knauff is a very talented, young offensive player with good speed and good dribbling," Zorc said at the time, with some predicting the pacey winger, who models his game on Kylian Mbappe, could be developed into a wing-back in Lucien Favre's favoured 3-5-2 formation.
He has, however, continued to be utilised as part of the forward line, playing predominantly from the left so as to be able to cut inside onto his stronger right foot, though in the first team he has been used on both flanks so far.
His form for the Dortmund 'B' team in the German fourth tier, for whom he scored seven goals and assisted six more this season, earned him a permanent call-up to the senior squad in March, though he had already made his first-team debut against Zenit in the Champions League back in December.
Now, with rumours yet again beginning to swirl around Sancho's future this summer, there could be a gap in the Dortmund squad for Knauff to exploit next season.
"I want to play as much as possible next season, but I'm not eyeing a place in the starting XI yet," he says. "I just hope that things will continue as before and I will throw all my effort into that.
"It would be great if I could then take another leap in my development."
If that proves to be the case for Knauff, the next time he starts a Champions League knockout game might not come as much of a surprise.