There were high hopes for Mbappe when he finally ended years of speculation by completing a statement move to Real Madrid on a free transfer last summer, after his Paris Saint-Germain contract expired.
The 25-year-old has scored on average a goal every other game for Los Blancos this season, netting nine times in 18 appearances across all competitions, but many feel that the Frenchman has failed to reach the heights expected on a consistent basis.
Mbappe has scored just twice across his last five La Liga appearances, with Real Madrid currently sitting four points behind leaders Barcelona who have played a game more.
Meanwhile, Real Madrid's new No.9 has only made the net ripple once in this season's Champions League and has now gone four games without a goal in the competition, after having a second-half penalty saved by Liverpool's Caoimhin Kelleher in a 2-0 defeat at Anfield on Wednesday night.
Patience is the remedy for out-of-sorts Mbappe
Ancelotti has acknowledged that Mbappe is going through a "difficult" period in front of goal and has offered the Frenchman some advice on how to get back to his best.
Speaking to reporters about Mbappe's form after the defeat to Liverpool, Ancelotti said: "It has happened many times that forwards have a hard time scoring. There is a medicine which is to be patient.
"It is a difficult moment for him, especially after missing the penalty. Everyone has to support him."
The Italian coach added: "He may be a bit lacking in confidence. When things don't go your way, the idea you have to have is to play simple.
"It's a bit like this moment, but you can't judge him for missing a penalty. All players miss penalties. He has to keep working well. We have to be patient because he's an extraordinary player."
McManaman: 'Mbappe flattered to deceive against Liverpool'
Mbappe was tasked with stepping up to provide the goods in front of goal against Liverpool in the absence of injured attacker Vinicius Junior, but the Frenchman failed to deliver according to ex-Real Madrid and Reds midfielder Steve McManaman, who believes former striker Joselu, 34, would have fared better at Anfield.
Speaking to TNT Sports, McManaman said: "They needed Mbappe tonight. Without Vinicius, without some of the other stars, he flattered to deceive tonight. That was his moment (the penalty).
"The press will be ruthless about Kylian because he didn't deliver again when needed to. Madrid are going through a rough patch and the big players are not playing well. It just magnifies it. Vinicius isn't here - will Kylian step up tonight? No, he doesn't."
McManaman has also questioned why Ancelotti has not used Brazilian starlet Endrick more amidst Mbappe's poor form, adding: "Mbappe's getting very frustrated actually because [Endrick] wants to play more. They've got enough centre-forwards but [Ancelotti] doesn't want to use them at this moment.
"They need a centre-forward tonight. Kylian is not a number nine - he might have it on his back but he is not a goalscorer supreme in those positions, is he? He likes to play out wide. They might as well have kept Joselu."
Mbappe will hope to quickly rediscover his form when Real Madrid take on Getafe in La Liga at the Santiago Bernabeu on Sunday.