That felt like a reference to Liverpool but, more importantly for United, it was also an admission that it will need a dramatic improvement this season for his own team to bridge the gap.
Timothy Fosu-Mensah - a contender to play at centre half, but most probably at right back, considering United's options - has arrived at Premier League newcomers Fulham to agree a season long loan after spending previous year on loan at Selhurst Park.
The Merseyside outfit have signed AS Monaco midfielder Fabinho, RB Leipzig star Naby Keita, Stoke City playmaker Xherdan Shaqiri and AS Roma goalkeeper Alisson Becker in the summer transfer window so far.
Mourinho sounded pessimistic that he would make any last-minute signings when talking to media on Thursday. It is time for me to stop thinking about the market because the market will be closed.
"You don't really know the team, you don't really know the players, you don't know how they're going to perform from one week to the next".More news: Lombok quake deaths rise to 91, "massive" damage
"My view is that, first of all, is hard for me to believe we finished second", he said.
"The target is Leicester match and the tactics to be changed in Championship Manager you can just press a button", he said.
The Red Devils coach has cut a sullen figure throughout pre-season with the former Chelsea boss unable to hide his dissatisfaction with Brazil global midfielder Fred being his sides only high profile signing.
"So I will have to focus on the players I have and in relation to these first couple of matches - maybe three matches because after Spurs (and Burnley on August 27 and September 1 respectively) there is (a) national team (break) and a couple of weeks to recover people and prepare people better".
'You are capable of making people who win nothing and finish below us look like serial winners.
With so much business being done since the end of last season, it has been tough to keep track of who has gone where.