Mourinho says he never got same support as Ten Hag at Man Utd
The Portuguese, who last managed Serie A side AS Roma before being sacked in January, was fired by United in December 2018 following a series of dismal results having won the League Cup and Europa League in the 2016/17 season.
Mourinho, who has also managed Porto, Chelsea, Inter Milan, Real Madrid and Tottenham Hotspur, added that there were still a few players at United who he did not want when he was there.
"What Ten Hag has in his time at Manchester United I didn't have. I didn't have that level of support. I didn't have that level of trust," Mourinho told The Telegraph.
"So I left sad because I felt I was in the beginning of the process.
"In some moments, I felt if they trusted me and believed in my experience, things could be different.
"There are a couple of players still there I didn't want five or six years ago. I think they represent a little bit what I consider not the best professional profile to a club of a certain dimension.
"But I did my job there. Time always tells the truth. I would love Manchester United to succeed."
Under Ten Hag, United ended a six-year trophy drought last season by winning the League Cup after the Dutchman joined the club from Ajax Amsterdam in 2022.
United are seventh in the Premier League, with British billionaire Jim Ratcliffe having struck a long-awaited deal in December to buy a 25% stake in the club and take charge of football operations to try to revive their fortunes on the pitch.
Mourinho, who is presently without a club, said there was still a long way to go in his managerial career.
"It is not like I am 61 and I want to stop at 65," he said. "No way at all. There is still a long career to go."