"He wants more at football's highest level, so we are having conversations and we are discussing the possibility of him staying with us for the second part of the season".
Mourinho told a news conference on Friday: "We have 25 percent left which means one of four - we got a central defender that can play many other positions which is very important".
Mourinho has indicated that he wants a fourth signing before the transfer window shuts on August 31, as he needs a winger to bolster his squad.
"I don't say I know the league better because I have been in this league for a long time".
"We have had a better pre-season than previous year and we have the confidence levels of a team that has won a European competition and returned to the Champions League".
The United manager had outlined four positions he wanted to strengthen in to executive vice-chairman Ed Woodward at the start of the transfer window, but only Victor Lindelof, Romelu Lukaku and Nemanja Matic have arrived at Old Trafford. It's not something urgent, it's nothing that you are desperate to have it done or not done.
Mourinho's side begin their Premier League campaign at home to West Ham on Sunday having enjoyed a strong pre-season, winning six out of seven friendlies before losing to Real Madrid in the UEFA Super Cup on Tuesday.
United will be without Luke Shaw as they defender continues to recover from a foot injury while Ashley Young and Marcos Rojo are also long-term absentees. We are going to try to win the title.
"There is no guarantee, but naturally a manager in his second season knows the club and the players better".
Mourinho says he is after another player "coming from the sides" to complete his summer business - leaving the door open for either a winger or a full-back.
"I think Tottenham, without any spending, are equipped to win because they have a fantastic team, fantastic manager, great stability".
"I am not a hard person to work with, and I understand the reality of the market". I want the Champions League to start.
"I understand the reality of the market, of the numbers and that my club by doing 75 percent of what I initially asked did very well". I will just go with everything.
"And last season that didn't happen much - we were focused on the goals that our striker was scoring and when he was not scoring, the team was a little bit in trouble to win matches". "But we have players and if we can not strengthen the team in these areas, we have players that we trust". I do think it will be a decent game but expect the hosts to edge it.