The French club are going through a rough spell, having lost three of their last five games in Ligue 1.
Ancelotti said his players "did not have a good attitude" in Saturday's surprise 2-1 reverse at mid-table Nice and he is looking for a much better display against Group A leaders Porto.
"This match is important for two reasons," the Italian told a news conference on Monday. "To finish top of the group and to end this (bad) period.
"We need to focus on the little details."
Ancelotti took over in December 2011 and spent a fortune on new signings in the close season, splashing out around 150 million euros ($196.07 million).
PSG though are down in fourth place in Ligue 1, five points adrift of leaders Olympique Lyon, and media reports suggest his job may be on the line.
"When you build a new team, there are always problem," said Ancelotti. "The pressure ahead of tomorrow's game is normal.
"We're not in a good period but I have a good feeling for tomorrow."
PSG's media officer asked for Monday's questions to focus only on the Porto game but, as the reporters refused to back off with concerns over his future, Ancelotti added: "I have not read the papers - I don't know what you are talking about".
Full back Maxwell, who joined from Barcelona in January, said the Paris club needed time.
"When you go through changes there are difficulties," he explained. "We are still in that process.
"We need to talk to each other and continue to work. There are always highs and lows in transition periods but we'll do our best to get through this rough patch."
Ancelotti's team, who lost 1-0 at Porto in October, have 12 points from five matches and trail the Portuguese by one point in Group A.
"PSG are a talented team but if they do not play as a team, they will not create chances," said Porto coach Vitor Pereira.