But the Denmark midfielder has said he could have joined the club years earlier and had conversations with United managers Louis van Gaal, Jose Mourinho and Ole Gunnar Solskjaer during his time at Tottenham from 2013-2020.
"I've spoken to every manager who's been here at Man United to see what the situation was," Eriksen, 30, said.
"But I was at Spurs at the time and I really couldn't see myself playing in another English team at that time. I went abroad and went to Inter.
"It's been on the books, well, not on the books but it's been spoken about. For me, it wasn't the [right] timing, it wasn't there and I was at a place at Spurs for a long time and I wanted to try something abroad and I went to Inter and ended up having a lovely time.
"But then obviously something happened in the summer and that changed a bit the career path I had in mind, and then obviously to come back to Brentford first of all and then to be here is something I didn't think could happen a year ago."
It has been a rollercoaster 12 months for Eriksen, who suffered a cardiac arrest while playing for Denmark at the European Championship last summer.
He was released by Inter Milan in December 2021 amid fears he might never play again but signed a short-term contract at Brentford in January.
After becoming a free agent in June, United signed him amid competition from Brentford.
There was also speculation he could return to Spurs but Eriksen said they never tabled an offer.
"It was only talk," he added.
"They never really came with anything so it wasn't really a thing for me to go back to Tottenham at the time and Man United were very early on, very positive and I had good conversations.
"It was very positive from the first few phone calls already and the club felt like they wanted me, so it was on for a long time."
Eriksen only began training with his new teammates last week but has built up his match fitness with minutes against Wrexham, Atletico Madrid and Rayo.
Ten Hag has another week to prepare his players ahead of their Premier League opener against Brighton at Old Trafford on Aug. 7 and Eriksen said he's fit and ready if selected.
"I feel good," he said. "I'm always most pleased when preseason has finished and the season starts and then you know your condition is where you hope it should be.
"It's been good, I've been taken good care of by the group and I've been getting my minutes in and I'm really trying to slot in as quickly as possible to the first-team."