The Italians could eliminate Atletico from the Champions League on Wednesday with a victory at the Wanda Metropolitano, while Simeone's men are struggling in La Liga too, fourth and 10 points behind leaders Barcelona.
However Monchi, who was previously at Sevilla, is convinced Atletico are undergoing only a temporary blip.
"Whoever thinks a Cholo (Simeone) team is dead, does not know him or Atletico," Monchi told Spanish newspaper AS.
"They have suffered a dip, but I am convinced they will be born again. The demand is huge at this level, the margin for error small and any moment of doubt seems bigger than it is."
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Atletico, who have only three points from four Champions League games, must beat Roma at home and Chelsea away while hoping one of the two slip up against Qarabag, if they are to progress from Group C.
(Reporting by Rik Sharma; editing by Clare Fallon)
