Speaking in the United States on the club's pre-season tour, Mourinho insisted he was uncertain if he would be adding to the signings of Lee Grant, Diogo Dalot and Fred.
He said: "I've no idea.
"I'm not going to lie to you, I'm not going to say somebody is coming or nobody is coming.
"We did Lee Grant because we have a fantastic young goalkeeper who needs to play football. Joel (Pereira) is a Manchester United goalkeeper but two years without football he has to play. And to protect that position we got Lee, experienced in the Championship, with Stoke City in the Premier League, so he is ready to fulfil that position.
"Joel is here with us, [it's] is good for him to play but then he will go on loan.
"Fred we did quite a long time ago, we started the process, we lost Michael Carrick and I think Fred is the kind of player we need to complement the qualities of our midfield players.
"Dalot is injured, a small injury, a small surgery, we didn't want to lose him because of that and he's recovering really well and we think he can start training back in England, not ready for start of the season."