And now it appears there is a way back at United, with Mourinho's comments suggesting he will be given the chance to return to the club.
"It's the objective of every one of the top teams and every one of the top team managers". "You know he's injured, he needs time to recover, he's not ready to play tomorrow".
"My teams always had the goalscorer - the guy that scores more goals - but then we had the winger that scored 15 goals, the midfield player that scored 10 goals and we had the central defender that scored five goals". If we manage that, we'll try to finish in the top two. "But to have a better position in table we need to win more".
Lukaku, Victor Lindelof and Nemanja Matic have been brought into help in to boost their title challenge, with the United boss looking to continue his remarkable record of winning the league in his second campaign in all five spells in charge of a major club.
He achieved the feat at Porto, Chelsea twice, Inter Milan and Real Madrid, with the only exceptions to the rule being his first two management roles, at Benfica and Uniao de Leiria, where he lasted less than a season in both cases.
"There's no relation between clubs and countries and seasons and periods, so obviously there is no guarantee".
"I don't think I am in a position to be moaning and crying".
"We just develop that and we played in a couple of matches, Sampdoria and I think the LA Galaxy, because it is something during the season we are maybe going to do".
He said: "It's not because I have always done it that I am going to do it".
"I have conditions to deliver a better team than I did in the first season".
"I don't say I know the league better because I have been in this league for a long time".
United were the lowest scorers of the Premier League's top seven last season with just 54.
"Last season we won trophies".
"Arsenal and Everton, they are in the Europa League".
"But if we cannot strengthen the team in this area, we have players we can trust".
Such absentees means the United boss does not believe they have advanced hugely compared with this time a year ago, but he retains hope of making a fourth summer signing.
"We have added three players, one defender, one midfielder and one attacking player", the Portuguese boss explained. "We were focused on the striker scoring goals and when it didn't happen we were in trouble".
Mourinho believes United's players - old and new - head into Sunday's Premier League opener against West Ham with "a positive feeling and great experience". We lost only one league match at home and in the cups never lost (at home), but there were too many draws.style="text-align: center;"