Ibrahimovic, 35, tore his anterior and posterior cruciate ligaments after a nasty fall in United's Europa League quarter-final clash with Anderlecht in April. "We would like two more but at least one".
Ibrahimovic has been linked with moves to former club AC Milan and Major League Soccer side LA Galaxy, while sources have told ESPN FC that United have not ruled out offering him a short-term deal if he can prove his fitness.
"So I don't want to say Matic or any other name because I don't think it's correct to do it".
But, speaking on United's own pre-season tour in the United States, Mourinho said: "He [Matic] is a Chelsea player".
Michael Floyd Suspended 4 Games by National Football League for DUI Arrest in December
The former Cretin-Derham Hall star had already spent 24 days in jail this spring after pleading guilty to extreme DUI in February. A source told the NFL Network that the Vikings were hopeful that the NFL would choose three games for the suspension.
Manchester United recruited Victor Lindelof in a £30.7m deal from Portuguese champions Benfica last month.
"Yes, we have had interest, that is obvious and it's public", Mourinho said.
A deal to bring Ibrahimovic to California is, however, fraught with problems, as Galaxy have already filled their the "designated player" berths in their squad for the 2017 season.
"He didn't want to hide behind an wonderful injury".
"He did not want that, he was not happy with his finish (to the season) and not playing". He is open. We wanted to be honest and open and give everything for him to make a decision, in case his desire was to leave.
The recent £75m signing of Romelu Lukaku would suggest that the role of main striker at Old Trafford has now been filled but if Ibrahimovic is prepared to accept a reduced role at the club there may yet be a place for him next year. He made the challenge for himself to keep playing at the highest level. Let's hope we seem him back in action in a shirt of his own choosing soon.