The self-proclaimed 'Special One' believes the task which faces him at Chelsea is harder than it was during his first spell, when he won two Premier League titles, and that winning the 2012 Champions League and 2013 Europa League merely papered over the cracks of an inconsistent team with a mental fragility.
Despite some impressive one-off results, the Blues finished sixth in the 2011/12 season - 25 points behind champions Manchester City - and third last term, 14 points adrift of Manchester United.
Mourinho said: "If you see the position of Chelsea in the last leagues and the difference of points from Chelsea to the champions, you can imagine that even with a magic click - that I don't have - it's not easy to recover 20 points. It's more than one click.
"For a club like us it's not good to be 15, 20 points behind.
"We need to win seven matches 1-0, not win one match 7-0 and lose the other six, or lose points.
"This is the kind of mentality that you have to build. And it's much more difficult.
"I had a team of players in the best moment, potentially, of their career (in his first spell as boss).
"I needed a click to make them believe. At this moment, in terms of building a team, the task is different."
Chelsea have won the league title once since Mourinho's departure - in 2009/10 under Carlo Ancelotti, who left the following season after finishing second, nine points behind Manchester United.
Source: PA
Source: PA