Steve McClaren’s side are just a point above the relegation zone after last weekend’s abject 3-0 home defeat to Leicester City.
Head coach McClaren and his players were booed at the final whistle on Saturday.
And McClaren is considering making changes for Saturday’s game against Alan Pardew’s 10th-placed Crystal Palace.
Cisse – who netted in a 1-1 draw between the two sides at Selhurst Park last season – is pushing for a recall to the starting XI.
And the striker said: “I understand that frustration because the manager himself too is not happy – neither are the players as well.
“During the game we didn’t play very well, and the fans are frustrated. The players understand that, because we did not play well.
“It’s the Premier League. It’s very, very hard every Saturday. Every game is very difficult.
“All through the week we try to work hard on the training ground to get a result on a Saturday and win the game, but, for me, Leicester were the better team.
“They showed it and they scored as well.
“Everything they did was very, very good and it was the opposite for Newcastle.
“The last five games we have shown it but not against Leicester. We just have to try to forget this game and focus on the next one.”
McClaren was furious with his team’s performance against Leicester, who went top of the league thanks to the victory.
And Cisse says the players can’t afford to let their heads drop ahead of the Palace game, which is followed by a tough home fixture against in-form Liverpool.
“I don’t like to say what the manager said in the dressing room,” said the Senegal international.
“That one is for the manager and the players, but the one thing I can say is we need to keep our heads up. It is not easy, and we need to try to work hard in the week and go and win the next game.”
Jamie Vardy scored for a 10th successive game to give Leicester the lead on the stroke of half time, and Leonardo Ulloa put the game beyond United just past the hour-mark.
Shinji Okazaki netted late in the match.
Reflecting on the game, Cisse added: “The game is very, very hard, and we tried to do some things
“But they pressed very, very high and they’ve a very good team.
“They have very good strikers, and they score with just about every attack, and they had more than us.”
“That second goal made the game very, very hard because they scored the second goal so early and we tried to score one to try to come back into the game.
“But after the third, I think at that moment the game was over.”