They will get their chance on Wednesday when Bayern tries to defend its 1-0 lead in the second leg of the round of 16.
Bayern won the first leg in Paris with a goal from former PSG player Kingsley Coman, but the team's approach in the return match will be closely watched.
Under Nagelsmann, Bayern tends to defend one-goal leads by trying to score two or three more. Keeping up the attacking pressure worked in the group stage against Inter Milan and Barcelona, neither of which could score against Bayern, but it could allow PSG opportunities to get back into the game.
“Both we and PSG have enormous pace in attack. We want to get at them when they take possession and be physically present from the first minute," Nagelsmann said Monday. "What we need in the second leg is to prevent them from using their pace. If you give their attackers too much space and they can unleash their footballing qualities, it’s incredibly difficult to defend.”
Either way, one of the two teams will face its earliest Champions League exit since both were eliminated by English opponents in the round of 16 in 2018-19. Bayern and PSG both expect to be in the quarterfinals at the very least, so a loss could affect the future of Nagelsmann or PSG coach Christophe Galtier.
Hiring Nagelsmann on a five-year contract in 2021 was a statement from the Bayern hierarchy that they saw the then-33-year-old German as the architect of a long-term project. He's now facing a tough challenge from PSG and also a tight domestic title race, with Bayern even on points with Borussia Dortmund in the Bundesliga.
Both teams are without key players ahead of Wednesday's game.
Sadio Mané missed the first leg with the leg injury which previously ruled him out of the World Cup, but the Senegal forward has since returned to action and came off the bench in Bayern's last two Bundesliga games.
Still, Bayern remains without goalkeeper Manuel Neuer and defender Lucas Hernández, both long-term absentees, and fullback Noussair Mazraoui is in training but has not played since the World Cup. Another defender, Benjamin Pavard, is suspended after he was sent off in stoppage time in the first leg and is set to be replaced by Josip Stanišić.
PSG is without Neymar after the Brazilian was ruled out for the rest of the season on Monday with an ankle injury, but Mbappé and Lionel Messi each scored in the 4-2 win over Nantes on Saturday. Mbappé became the club's all-time leading scorer with 201 goals, breaking a tie with Edinson Cavani.
Right back Achraf Hakimi is in PSG's squad for the game after he was given preliminary charges in a rape investigation last week. The 24-year-old Hakimi missed the last three French league games with injury.
In the French legal system, preliminary charges mean judges have strong reason to suspect a crime was committed but are allowing time for further investigation before deciding whether to send a case to trial.
Speaking Tuesday in Munich, both PSG midfielder Marco Verratti and Galtier said they expect a completely different match than last month when Bayern’s pressing suffocated PSG.
Verratti said the return to a tactical system with three defenders will certainly help, as well as the presence of a fully-fit Mbappé alongside Messi.
"They are players of a huge experience, that is something that really helps us out,” Verratti said.
Mbappé was only able to play half an hour in the first leg as he just returned from injury. Now fully fit and in full confidence, Galtier expects the France striker to provide extra solutions.
“That will give us more scope to get behind,” Galtier said. “We need to have more possession, play higher and win the ball much faster.”
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