The factory Ducati rider leads Pramac's Jorge Martin by 21 points in the championship coming into the finale in Valencia.
But his weekend got off to the worst possible start, as Bagnaia struggled to 15th in practice and missed the Q2 cut while Martin sailed through in second.
Bagnaia says he was losing half a second in just three corners due to issues getting his Ducati stopped, but thinks it is "fantastic" that this is the case, rather than that time loss being across the whole lap.
"I was struggling. It was not an easy day from the start," Bagnaia began. "I struggled a bit with brakes at the start of FP1 and then we put in something different and I was feeling OK.
"But my feeling today was not the best on the entry of the corners. I was always having a lot of locking and losing a lot of feeling.
"But honestly, checking the data after the time attack, I lost five tenths in three corners. So, it's easier to understand where to improve like this, but five tenths in three corners is a huge amount of time.
"We will improve for tomorrow. For sure, normally we have time and we finish the job on Friday already. And this time we need more, so tomorrow morning will be a very important session."
When asked if his nerves were worse than they were at the same stage of the season last year ahead of his first title win, he added: "I have to say that it's better right now.
"I don't know if just right now I have to think on improving my feeling. But last year I was struggling more with the pressure.
"Last year I was more nervous. Today I accept that we have problems, today I accept that we have to work.
"We already checked many laps on the data and I'm happy that the amount of time that I'm losing is just in three corners. This is fantastic."
The final 10 minutes of second practice saw the title rivals close on track, with Martin repeatedly following Bagnaia.
Bagnaia says he is "used to" this happening, but feels Martin should focus on his own job rather than engaging in mind games.
"I'm used to it, honestly. All the season it's the same, and the last three races Jorge started to do the same," he said.
"Honestly, I was quite slow to be in Q2, so I was expecting to not be competitive.
"I tried to do the maximum and it wasn't enough. About Jorge, it's a bit better if he starts thinking on his job because he said he needed to win both races.
"And like this he is losing time to be focused on his job. Right now he's not the fastest, so it's better that he improves a bit."
Bagnaia once again kicked back at the suggestion of needing team orders and noted that he was able to win in Indonesia when he started from 13th.
"I don't like team orders and I think we have the potential to be in Q2," he noted. "I will try to do the maximum. In case I won't be in Q2, in Mandalika I was P13 and I won the race. So, we will try to do the maximum."
