The 35-year-old Ibrahimovic scored 28 goals before a serious knee injury brought his first season at Old Trafford to a halt in April.
"He's injured and he needs time to recover", Mourinho said on Friday.
'Obviously [we wanted] a player for another position playing from the sides, but we have players and if you can not strengthen the team in these areas, we have people that we trust and we go for it'.More news: Trump speaks with Guam governor amid North Korea threat
"I just think that naturally, a manager in the second season knows the players and knows the club better".
"I don't think I'm in a position of crying, moaning, protesting".
And Mourinho, speaking ahead of his side's Premier League opener against West Ham, noted that his side has what it takes to challenge for the title.
"But I am not a hard person to work with, in spite of sometimes it looks different or you want to make it look different. I'm really happy to start the Premier League this weekend because our pre-season was very complete and was a pre-season organised in a way where we start playing MLS teams and ended playing against the best teams in Europe". I'm not in a position to say I'm not happy. United have also been linked with Inter Milan wide attacker Ivan Perisic over the summer and still appear to be interested.More news: Piers Morgan reacts to Arsenal's 4-3 win over Leicester on Twitter
"But we have players and if we cannot strengthen the team in these areas, we have people that we can trust and we go for it".
Is Mourinho set to continue his title winning sequence at United this season?
"Europa League is not Champions League", he said. "But the top seven, we are going to be in the four competitions and so there is no advantage for any one of us".
The ex-Chelsea boss threw his winners' medal into the crowd following their Premier League triumph in 2006 and also gave away his medal following the 2015 Community shield.More news: Sammy Watkins is headed to the NFC West
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