Reflecting on his time in Manchester via a video posted on his Instagram, the 31-year-old claims he knew very quickly he wasn't going to enjoy his time with the club and hit out at the squad's lack of unity during his time there.
"After the first training session I realised many things, I came home and asked my family and my manager if I could not break the contract and return to Arsenal, something did not fit me, but I had already signed," Sanchez said.
"Months passed and I kept feeling the same. We were not united as a team at that time.
"The journalists also spoke without knowing and it hurt. Former players also spoke and had no idea what was happening inside the club. And they hurt me.
"A player also depends on the internal environment, that we need to be a family. We weren't like that, and it was reflected on the field. If someone had to be blamed, they blamed me.
"I do self-criticism and should have played better. But I was always blamed, even if I played for a few minutes."
Sanchez ultimately made 45 appearances for the Red Devils, scoring just five times and contributing nine assists - statistics that pale in comparison to the 80 goals he struck across 166 games with the Gunners.
Manchester United manager Ole Gunnar Solskjaer recently conceded Sanchez simply failed to play to his full potential while at United.
"We wish him all the best and he is a top player who we want to see play his best football," Solskjaer said.
"For whatever reason we didn’t see the best of him here, but he’s a top professional and we wish him all the best."
Former Red Devil Paul Scholes wasn't so kind in his farewell for the Chilean attacker, noting that the club should have arranged an exit sooner.