The Bavarians dropped to second place, a point behind Dortmund, after last week's 3-1 loss to Mainz. They face bottom club Hertha Berlin on Sunday.
The side have struggled since Tuchel replaced Julian Nagelsmann as manager, winning just one of their last six matches.
Nevertheless, the coach remains optimistic about his side's title chances, confident that they will imrpve.
"The situation has become more difficult for us now but it is not hopeless," he told a news conference. "I still have the feeling we will shift up a gear (in the last five games)."
Since his arrival in late March, Tuchel has seen his team crash out of the German Cup and the Champions League last eight while also giving up the lead in the Bundesliga.
Tuchel will be without Dayot Upamecano for the game after the France defender picked up a muscle injury in training this week and will be sidelined for about two weeks, the coach said.
Hertha are in last place but have brought back former coach Pal Dardai in a last-ditch effort to avoid relegation.
"They are a bit unpredictable now with the coaching change," Tuchel said. "We have to reduce expectations and not expect too much from ourselves too early."
"We have to take it one minute at a time and eventually reach the win. But we have to deliver. Talking about our situation in the standings at the moment does not really make sense."
"We are very honest. We are the last ones to sweep anything under the carpet. We have dropped five points in the last two matches," he said.
Dortmund, in top spot on 60 points, take on VfL Bochum later on Friday and could open up a four-point lead before Bayern's game on Sunday.
"I don't know if I will watch it," Tuchel said of the Dortmund game. "It brings us nothing. Our situation is very clear. We have to get 15 points. Now it's only about us."
