The former Atletico Madrid marksman insists he never had any issues with Louis van Gaal during his wretched loan spell with the Red Devils during the 2014/15 campaign
The Colombia international joined United on loan from Monaco in September 2014, but the club did not make the move permanent after he scored just four times in 26 Premier League appearances, 14 of which were starts.
Falcao, 30, has since joined Chelsea on loan for 2015-16 and had even fewer opportunities with the champions - only nine league outings and one start - due to injury problems.
Reflecting on his time with the Red Devils, though, the striker feels he never had the opportunity to gain momentum due to being put in and out of the team by Louis van Gaal.
Falcao told El Tiempo: "It was complicated in Manchester. Everyone saw how there were situations which created instability, since I played on some days, not on others.
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"It was 60 minutes today, then 45, then 20 - that generates instability and sometimes you don't know where you stand or what the footballing preferences of the coach are.
"It's been difficult. I had been used to playing regularly. After the knee surgery [at Monaco] I went to Manchester United, who were starting a new process after 25 years with the same coach, with a lot of new players and I did not have the opportunity I expected."
However, Falcao insists he did not have any major personal clashes with Van Gaal and found the dressing room atmosphere to be normal and professional.
Asked if there were problems with the Dutchman, he said: "No, not at all.
"Yes, we had the usual discussions of a football team, with the same arguments, but it was always with respect and at no moment was there any kind of problem."