The 48-year-old was brought in to mentor United's number one after working closely with the goalkeeper during his time at Atletico Madrid but after three years at the club, Alvarez left Old Trafford in October last year.
It was initially reported that De Gea's 'dip in form' prompted questions about Alvarez's methods within Ole Gunnar Solskjaer's coaching set-up.
It was also understood his relationship with other coaches had become strained before his departure but now, the former United coach has opened up about the situation, citing De Gea's lack of loyalty in an extraordinary interview.
"It's not true that Manchester United relieved me of my duties." he told Spanish publication AS.
"In fact, once De Gea renewed, United put an offer on the table for me. It was me who asked to meet with the club so I could tell them I wanted to leave the club.
"It was at this meeting they asked me to renew. I told them I was going but not because I wanted to leave United. I wanted to stop coaching De Gea.
"Aside from being his mentor at Atletico Madrid, where I backed him strongly, I was the person who convinced him to sign for United. I was his right-hand man in Manchester.
"I came to United thanks to the great work of Jorge Mendes and because [Jose] Mourinho wanted to sign me to help David develop and to keep him at the club. At that moment, he wanted to leave United."
It must also be noted that De Gea signed a new contract at Old Trafford, just two weeks before Alvarez's departure.
His decision to extend his deal at the club 'behind his back' has been labelled as 'a lack of loyalty' by Alvarez.
He added: "After almost three years with lots of work and meetings with United to renew him and to make him the best paid player in the world, I learned that he had renewed behind my back. Honestly, it felt like a lack of loyalty."
"During negotiations, he also had a falling out with the person who had carried out all the talks in order for him to be paid what he was paid. At the last minute, someone else meddled. I insisted that I didn't like that because it seemed disloyal.
"I asked David why he didn't say anything to me and he said that he was told not to say anything to anybody. This had an impact on me.
"The way I understand my profession is that you can't help someone develop if you do not have total confidence with them and that's why I decided to leave United."
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Featured Image Credit: PA
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