John Terry's second-half own-goal was enough to hand Palace a victory that eased their relegation fears and led Mourinho to claim it is "impossible" for his side to win the title.
And Mourinho believes their London rivals were more up for the fight at Selhurst Park.
"They (Palace) had a strong mentality, were aggressive, committed and everyone of them played at the top of their potential and in football (that) is important.
"Clearly we have some players that because of their profile, they find it difficult to perform in some high-profile matches.
"You have (Branislav) Ivanovic, (John) Terry, (Gary) Cahill and (Cesar) Azpilicueta and they play in the sun and the rain and they perform every game.
"Then you have other players that are fantastic in some matches, but they disappear on other matches."
The setback led Mourinho to once again play down his side's title hopes.
"We depend too much on other results, when you depend a little it's possible when you depend a lot I don’t think it's possible," he said.
"I know mathematically it is still possible but one thing is mathematic the other is reality and I think it is too much."
The former Real Madrid boss also threatened to make changes for the clash with Paris Saint-Germain in the quarter-final of the UEFA Champions League on Wednesday.
He added: "If they have their mind in Paris then they maybe have the risk of not playing in Paris."
