In addition to his reputation as a tactical mastermind and expert motivator, RB Leipzig coach Julian Nagelsmann is known for his ability to upgrade high-quality professionals into world-beaters, with the likes of Dayot Upamecano, Angelino and Marcel Sabitzer already among the beneficiaries at the club.
Having previously transformed Niklas Süle, Sebastian Rudy, Kerem Demirbay and Sandro Wagner into full Germany internationals at former side Hoffenheim, Nagelsmann has also been working his magic at the Red Bull Arena since arriving in summer 2019.
bundesliga.com takes a closer look at the five players to have made the biggest jumps on his watch...
1) Dayot Upamecano
Before Nagelsmann: Signed from Red Bull Salzburg as a talented but raw 18-year-old in January 2017, Upamecano was considered one of the most prized up-and-coming defenders in the game. Strong, quick and able to play the ball out from the back, in 2019 Robert Lewandowski name-checked the Frenchman, alongside fellow Leipzig centre-back Ibrahima Konate, as among the best defenders he had faced. Not bad for a player yet to turn 21. However, he was a little rough around the edges and suffered from occasional lapses in concentration.
Since Nagelsmann: The fact that Upamecano has broken into the defence of reigning World Cup champions France tells you everything you need to know about his quality. Despite fierce competition for places alongside Raphael Varane, Samuel Umtiti, Clement Lenglet, Presnel Kimpembe and Kurt Zouma, among others, the Leipzig No.5 made his senior international debut in September 2020, and scored on his second appearance.
Not only that, but he has developed into the fastest centre-back in the Bundesliga in 2020/21, and eighth fastest player overall, with a top speed of 22.01 mph (35.43 km/h). Furthermore, he is the undisputed leader of the meanest defence in Germany’s top flight, having only conceded 21 goals after 26 rounds of matches. It is no wonder, then, that Bayern Munich swooped to sign him from summer 2021.
Watch: Why Bayern Munich signed Dayot Upamecano
So what has changed? Upamecano himself has said that he is "very happy to work with Julian Nageslmann," and that he has "improved enormously under him". In concrete terms, that has translated to eradicating errors and improving decision making.
"The mistakes he makes all start in the same way," said Nagelsmann of the Frenchman in November 2020. "As soon as he wins the ball he wants to give it to an attacker straight away, but that's not always possible.
"I see it as a learning curve. He needs to recognise when he can play the ball forward and when he can't. He's used to getting it forward quickly in order to start a counter-attack. That's how he's grown up in Leipzig these last few years when that was the main tactic. Now he needs to take the next step."
It's safe to say that he has: Upamecano has helped Leipzig keep clean sheets in eight of the 14 league matches he has played in since Nagelsmann made that comment, keeping the side hot on Bayern's heels in the title race.
Position: Left-back / left wing-back
Before Nagelsmann: Deportivo La Coruna, Manchester City, New York City FC, Mallorca, Breda, PSV Eindhoven... Angelino had played in four countries across numerous loan spells by the age of 22, never spending longer than 18 months in one place as he sought to establish himself as a top-flight professional. An impressive season in Eindhoven in 2018/19 was enough for Pep Guardiola to recall the 5'6" (1.71m) left-sided specialist to Manchester, but the Spaniard was never given a run in the team to prove himself.
Since Nagelsmann: The Leipzig coach recognised something others had not, however, and signed Angelino on loan twice, first for the second half of 2019/20 and again at the start of the current campaign, before his move was made permanent.
"To be honest, I'm here because of Nagelsmann, I signed on again because of him," Angelino said at the start of this season, and there is certainly a sense of mutual appreciation with his boss.
The 24-year-old has been a mainstay of Leipzig's side this term at left wing-back, and even though he has missed the team's last four Bundesliga games due to a muscle injury, he has still played more minutes (1,877) and made more sprints (560) than any of his teammates in 2020/21. He also remains fourth in the league overall for crosses from open play (81) - a metric that, alongside his four goals and four assists, underlines his relentless attacking intent.
Watch: Angelino under the tactical microscope
And as is the case with Upamecano, Angelino's improvement is partly down to being given specifics to work on. "He's expecting me to score seven or eight goals this season," Angelino said of his coach. "I told him I thought that was quite a lot, but now I've already got half of them."
Nagelsmann is keen for him to make progress at the other end of the pitch too. "In terms of defending while pressing, he's developed enormously," the 33-year-old tactician said in February 2021 of the Spaniard, who was named in UEFA's 23-man Champions League squad of the season for 2019/20, chosen by a panel of technical experts including Roberto Martinez, Gareth Southgate and Phil Neville.
"He's a very attack-minded 'full-back', in inverted commas, if you can even call him a full-back. In our own defensive third, he can still be a bit more solid defensively, because he's so attack-minded.
"This isn't even the best Angelino we're going to see; he's still got potential. I can't promise it, but I think I can say with a high degree of probability that he can still get a lot better. I've got a couple of ideas, along with my coaching staff, about how to improve him and I think we'll see that in the coming years."
3) Marcel Sabitzer
Position: Central midfield
Before Nagelsmann: Sabitzer is slightly different to Upamecano and Angelino in that he was not an up-and-coming youngster but already an established, senior international by the time Nagelsmann arrived. Able to operate as an attacking midfielder or from the right wing, Sabizter was already a regular in Leipzig's starting line-up, had made his Austria debut in 2012 and was named as his country's Player of the Year in 2017, ending David Alaba's six-year stranglehold on the prize.
Since Nagelsmann: Yet such are his coach's gifts that there is seemingly no putty he cannot mould. Sabitzer scored four goals and registered five assists in 2018/19 from an attacking role, but upon arrival in summer 2019, Nagelsmann decided to position him slightly deeper on the pitch, citing his lack of chance conversion as one of the reasons.
He instead deployed Sabitzer in central midfield, and has since hailed his stability and consistency in executing the role. "With some players, you never know if you can count on them," Nagelsmann explained.
"Sometimes they're good enough to play for Real Madrid, and the next game they're not even good enough for the reserves. [Sabitzer] stands out because he always plays well and is completely stable."
Stability and consistency might be enough for some, but in his relentless pursuit of excellence, Nagelsmann has continued to push Sabitzer to be effective in front of goal. He has chipped in with six league goals and two assists in 2020/21, and often makes late runs into the box; his 41 efforts on goal this term are more than any other defensive midfielder in the Bundesliga.
The Leipzig No.7 has also kept his knack of scoring long-range stunners, netting the Bundesliga's Goal of the Month in February with a sensational effort against Hertha Berlin on Matchday 22. Twelve of his 30 Bundesliga goals have come from distance, a figure higher than any other player since he arrived in the top flight in 2016.
"He's developed massively," said Leipzig sporting director Markus Krösche last year, an opinion evidently shared by the rest of the team, who voted him as captain at the start of the current campaign.
"Sabi frequently led the team onto the pitch as captain last term owing to the injury to Willi [Orban]," Nagelsmann said. "He showed in decisive games that he's willing to shoulder responsibility. [Being voted captain] is evidence of his good performances."
Now among the most highly prized central midfielders in the world, it is no surprise that he joined Angelino in the Champions League Team of the Season last year.
Watch: How Marcel Sabitzer compares to Bayern Munich's Joshua Kimmich
4) Tyler Adams
Position: Central midfield
Before Nagelsmann: Adams spent most of his debut Bundesliga season in the treatment room, playing just 10 league outings before Nagelsmann arrived. He was already a full USA international by then and had a reputation as a versatile player able to do a job in a variety of positions across the pitch.
Since Nagelsmann: He missed a big chunk of last season, too, but started 10 of his 14 Bundesliga appearances and also scored the crucial goal against Atletico Madrid that sent Leipzig into the Champions League semi-finals.
Adams has managed to stay healthy so far in 2020/21 and that, coupled with a long-term injury to fellow defensive midfielder Konrad Laimer, opened the door to him for an extended run in the side. He has gelled well with Sabitzer as a shield for the backline - although the 22-year-old has also played at centre-back and in right midfield - and he is the fifth-fastest player at the club after Upamecano, Justin Kluivert, Alexander Sörloth and Lukas Klostermann with a top speed of 21.3 mph (34.29 km/h), while he is second only to Angelino in terms of sprints made (546).
Watch: Former Leipzig chief Ralf Rangnick talks up Tyler Adams
Once again, Adams has taken on board some concrete pointers from Nagelsmann - notice a trend here? "The coach told me that he wants me to see me winning lots of balls," the 12-time USA international told Sport Bild at the start of 2020/21. "He also wants me to use my qualities to control the game or to speed up the tempo by playing the ball into dangerous areas."
Fast forward a few months, and Nagelsmann was lauding those very traits after his side edged out Wolfsburg in the DFB Cup quarter-finals at the start of March: "Both of them [Adams and Sabitzer] dealt with a lot of balls, and they were great with the distribution. I was incredibly satisfied. They both did a top-notch job. I want to praise Tyler briefly as he's been a stable force for weeks."
Tactically, too, Adams has developed a deeper understanding of the game, having adapted from the system employed in his first season at the club. "Under Ralf Rangnick, we played almost the same football," the New York native told Sky Sports.
"Now, under Julian, we play a variation of the idea that we once had. We don't lose the defensive side of our game, the quick transition, the pressing moments, but with the ball we are much stronger. We can keep it in difficult moments, pass our way out of certain situations.
"That is where Julian's tactical ideas really come into play because he wants us to be brave on the ball and take risks. He knows that sometimes it is not going to pay off and we might not succeed, but he is not afraid of us making mistakes. He trusts us."
5) Lukas Klostermann
Position: Right-back / centre-back
Before Nagelsmann: One of the longest-serving players at the club, Klostermann arrived at Leipzig when they were still a Bundesliga 2 side in 2014. Diligent and quietly effective, he spent the vast majority of his career at right-back and became a full Germany international in March 2019, becoming Joachim Löw's first-choice in the position after Joshua Kimmich's switch to midfield.
Since Nagelsmann: Klostermann's transformation has been similar to that of Sabitzer's in that it has involved a positional change. Nagelsmann's preference for a three-man backline has led to the 6'2" defender filling one of those centre-back roles: 19 of his 31 leagues outings last season were at the heart of Leipzig's rearguard, while all 16 this term have been there.
Strong in the tackle, quick on his feet and calm in possession, his lack of matches is merely due to a knee injury that kept the No.16 out of action between October and December last year, but otherwise, he starts when fit for both club and country.
"Lukas has made unbelievable strides in his development in his time with his," said Krösche when the player's contract was extended for four years in May 2020. "He can play in a number of positions in defence and that gives us a lot of flexibility. Lukas is very important for us and we're certain his importance and status will only continue to grow."
Nagelsmann has praised Klostermann for being "highly intelligent" and put his development down to a willingness to listen and try new things.
"I just love players like him," he explained. "They're uncomplicated, and he also always performs very well. I'm happy that I have him. You always have players in your squad where you ask, 'can you play on the left today?' They reply saying, 'No, I don't feel comfortable there, I'd prefer to be on the right'. But with Klosti, he just says, 'Okay fine, I'll play on the left today'. He does whatever the coach asks of him.
"If I were to ask him to run up and down the steps at the Red Bull Arena 25 times, he wouldn't ask questions, he'd just do it, come back, say he'd done it and then ask, 'what's next?'"