The 21-year-old joined Chelsea for £40 million last summer after a very public falling out with Ruben Amorim, which included a confrontation in front of the squad, social media posts from his brother criticising the manager, and Garnacho's own display of frustration after being used as a late substitute in United's Europa League final defeat to Tottenham.
Speaking to Premier League Productions, he admitted regret over how the situation unfolded.
"Maybe yes, because I loved that club. They gave me the confidence from the start, from Spain, to bring me to the academy, then they bring me to the first team, so it was like four or five years, and amazing love from everyone, from the fans, the stadium, everything was really good."
He was clear that the desire to move on was real, even if the way it happened was not.
"It's just sometimes you have to change for the good of your life or the next steps. I only have good memories of Man United."
On his final months at Old Trafford, Garnacho was unusually candid about his own conduct.
"I remember in the last six months I was just not playing like before at Manchester United. I started to be on the bench, it's not a bad thing, I was only 20 years old, but in my mind it was like I had to play every game."
He did not try to deflect blame.
"In my mind, maybe it is also on me, I started to do some bad things. But yes, it was just this moment in life and sometimes you have to make decisions and I am really proud to be here and still in the Premier League at a club like this."
Life at Chelsea has not been the fresh start he envisioned. He has scored just one Premier League goal in 20 appearances, and with Liam Rosenior taking charge in January following Enzo Maresca's sacking, his path to regular football remains unclear.
Garnacho, however, held no grudges.
"Everyone knows the team we have and the things we can do. Sometimes, we have better moments or worse moments, I am proud to be here but with United, I have nothing wrong to say about the club, no one in the club or the team-mates. It's just a moment in life that changes and life continues. I have no regrets."
The words carry a different weight now. At 21, with Chelsea reportedly open to selling him this summer, the boy who blew up his United career over a substitution in a cup final is still working out what comes next.