Los Blancos face Barcelona in the Copa del Rey before taking on the same opponents in La Liga on Sunday. They then complete a trio of crucial encounters when they travel to Old Trafford for the second leg of their Champions League last 16 tie against Manchester United, which stands at 1-1.
Defeat in all three of these games would leave Mourinho's side with nothing to play for for the remainder of the season as they would be out of both cup competitions and 19 points behind Tito Vilanova's side in the league, and Menotti believes this scenario would signal the end of the former Chelsea coach's time at Santiago Bernabeu.
"If Madrid are out of everything in these next few weeks, Casillas becomes the figure and Mourinho will have to go," he told Grada360.
"Football has these rules that are the same for everyone. The abuse as a coach can be handled only when you are a champion.
"All that power is only given to you for success, you do not get it if you don’t get the wins and the glory. That is what sustains the likes of Del Bosque and Guardiola."
Menotti, who also coached Atletico Madrid and Argentina in his distinguished career, commented on the differences between Barcelona and Real Madrid ahead of Tuesday's encounter, and believes Los Blancos rely too much on Cristiano Ronaldo.
"They [Real Madrid] have great players, but are different to Barcelona. Tactically they are a team that fights, that closes out the space well, but in the creative aspects of the game has a huge dependance on their players.
"Then, they have Cristiano, who is a barbarian who can win games. And if he plays well then they win. They achieve much, but when they do not have him to rely on, the team plays with 10 men."Both teams will want to win, but it looks like Barcelona are the collective and Madrid are the individuals."