Showing few signs of rust despite only returning to training this week, the World Cup victor, wearing the captain's armband, impressed in possession and without it, leading by example and keeping his cool from the spot.
His message sparked a flurry of tweets from United fans looking for hidden meanings, with some seeking reassurance that the player was settled at Old Trafford and not likely to jump ship to Barcelona.
"I had my plans for many months and I find myself with the market closed in a situation I did not think I would be in", Mourinho said.
Other fans were not so sympathetic.
"There are things and there are things that I can not say otherwise I will get fined".
Leicester forced attack after attack, but each one failed to bring the foxes equal.In his debut in the Premier League, youngster James Maddison, who signed this summer from Norwich city, looked very impressive.
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"It will be a hard season for everybody, not just for us", said Mourinho. "We thought maximum (he could play) 60 minutes, but he managed 80".
"If he upsets too many players because of his way, then ultimately he will lose his job like he did".
"I had only two options, Scott [McTominay] or Paul, but if I play Scott I play two two kids and a new player, so I asked Paul and he put himself available for the team and he was very, very good for us".
Manchester United will be aiming to try and win the Premier League title this season after they finished second and without a trophy last term under Mourinho. Paul [Pogba] was fantastic - his contribution was awesome, but the fuel was disappearing every minute, so we were in trouble and we needed [Scott] McTominay and [Marouane] Fellaini to give me that balance in midfield.
But it is not just the manager's relationship with United's players that has come under inspection, considering he was irked by executive vice-chairman Ed Woodward failing to strengthen the squad before the transfer deadline.
Mourinho was also quoted by the Daily Mail as saying that Pogba had come back with a desire to work.
"I mean, Manchester United, we have to show on the pitch, we have to play well, we have to be focused and we need people to trust us".