The Bavarians are far from their best, having managed only one win in their last five games across all competitions, with Tuchel set to leave at the end of the season, a year earlier than his contract.
They stumbled to a 2-2 draw at Freiburg on Friday to drop 10 points behind leaders Bayer Leverkusen in the Bundesliga.
"I think the situation for us is very clear but for a top performance there needs to be a certain pressure," Tuchel told a press conference.
"Our most recent results, including the first leg loss in Italy, mean that this won't feel super-easy tomorrow. Pressure is necessary. It will be there tomorrow."
"We need to win by two goals against an Italian team, a Maurizio Sarri team. The bar is high," Tuchel said.
The Bavarians, who have won the past 11 domestic league titles and clinched their most recent Champions League trophy in 2020, are at risk of going without any silverware this season.
Failure to advance on Tuesday in the Champions League could also potentially mean an even earlier departure for Tuchel.
"Not from my side," said the coach when asked if Bayern's potential elimination could mean an immediate exit for him.
"I know what we have agreed on and what we have communicated but you can be sure there is no one who has more ambition than me to win the game tomorrow," added Tuchel.
"Tomorrow every minute will count. Patience yes, if it is about not getting frustrated if things take a bit longer. Patience no, if it is only about generating possession. We have no time to waste," he said.
"Time is on Lazio's side so we need to play with a cool head but still have emotion and with emotion step on the gas and play for goals."
