The Setubal-born boss returns to Benfica on Wednesday evening, where he launched his glittering managerial career 17 years ago.
Mourinho was briefly in charge of the 36-time champions of Portugal after being assistant to Jupp Heynckes, who is now back at Bayern Munich.
But after only 11 games in charge of the Lisbon club – he won six and lost only two – Mourinho resigned when he was denied a contract extension.
Benfica’s decision not to offer him a new deal is one they have come to regret, given his incredible success.
And Mourinho is targeting even more glory after leading United back to the Champions League through last season’s Europa League triumph. His current club have been champions of Europe on three occasions, the first time being in 1968 when they beat Benfica at Wembley.
10. Tapping up Ashley Cole – Mourinho played a key part in Chelsea signing out-of-contract Cole from Arsenal in 2006, and his meeting with the defender in a hotel in London was deemed an illegal approach by the FA
“Benfica are our main opponent in this group”
Manchester United boss Jose Mourinho
And he wants his United side to be on a par with the teams of Sir Matt Busby and Sir Alex Ferguson who became kings of the continent.
The United boss said: “This club will always be a giant but our job now is to bring the football team back to that stature.
“I want the team to be on a par with the club’s history.”
“We will take that process step-by-step and be humble.
“If you are in the top two of your group you are in the Last 16 and anything can happen. However, we will not underestimate anyone in our group.”
United face Benfica in Lisbon on Wednesday and Mourinho is taking nothing for granted.
That is despite the fact they have won their first two group matches while his former club have lost both of their openers.
And those results for Portugal’s champions included a shock 5-0 battering in Switzerland against Basel.
But as United prepare to play Benfica away and at home in their next two European matches, Mourinho said: “The defeat suffered in Switzerland doesn’t change my
opinion that Benfica are our main opponent in this group.
“Benfica’s bad start in the Champions League doesn’t change the approach to the double match that is at the door.
“I believe they are better than CSKA Moscow and Basel.”
Wednesday’s match is a quick return to Benfica for United’s Sweden centre-half Victor Lindelof, 23.
He moved to United in the summer from the Estadio da Luz for £31million.
And the defender, who has played against Basel and CSKA in the Champions League so far season, said: “I had nearly five years at Benfica, so for me to leave was a hard decision.
“I was happy there and I developed a lot as a player.
It was great for me playing at Champions League level – I learned a lot from those games.
“But when the opportunity came to join Manchester United it was very easy for me to pick that option.”