Both Nagelsmann, 32, and Atletico's Argentinian boss Simeone, 50, are notorious for passionately urging their team on from the sidelines.
Nagelsmann wants to avoid falling "under the spell" of any heated emotions during the game in Lisbon, "but will concentrate on the (match) content, on the team".
"You're better off doing that than getting into an in-fight."
Leipzig, who are backed by Austrian energy drinks giants Red Bull, were only founded in 2009 and are in the knock-out phase of the Champions League for the first time having beaten last season's finalists Tottenham in the last 16.
Without the crowd masking any pitchside noise at the Estadio Jose Alvalade Nagelsmann is aware that his duel with Simeone will be even more intensely scrutinised.
"Now without spectators, you will be able to hear even more that he is always pointing things out, discussing a lot with the referee and demanding the use of cards," said Nagelsmann.
His Leipzig players are aware that things could get heated.
"I'm curious to see how things will work out with Julian and Diego Simeone," Leipzig defender Marcel Halstenberg told Sportbuzzer.
"They are both very emotional blokes."
Certainly, Nagelsmann has lots of respect for Simeone who has repeatedly steered Atletico to Champions League success after nearly a decade in Madrid.
"He wants to be successful. That's what sets him apart" said Nagelsmann.
Atletico are hoping to finally prevail in the Champions League final at the third attempt after losing to Real Madrid in both 2014 and 2016.
They have also won the Europa League twice under Simeone in 2012 and 2018.
"My colleague," Nagelsmann told Goal.com in reference to Simeone, "must have an extraordinary gift.
"I believe that 99 per cent of coaches who would always play 4-4-2 in such an aggressive fashion would be burned out after two years, but not him."
Simeone "runs around like dynamite and still gets great feedback from his players", added Nagelsmann in admiration.
Bayern Munich defender Lucas Hernandez, who spent five years under Simeone, vouches that the Argentinian's mentality was "visible every minute and in every training session".
Nagelsmann says such pitchside passion comes across as "a certain degree of craziness", which he finds appealing, but come Thursday he will try to ignore what is happening on the Atletico bench.
Atletico defender Sime Vrsaljko and winger Angel Correa both tested positive for coronavirus over the weekend and were isolated.
However, the quarter-final will go ahead after the entire Atletico squad and staff have since returned negative tests.