The former Sweden global scored 28 goals for the Red Devils last season before suffering a knee injury against Anderlecht in April.
The Red Devils coach has confirmed United are in talks with Ibrahimovic about signing a new deal once he is fully fit.
'He is injured and he needs time to recover, ' said Mourinho.
But Mourinho, speaking ahead of the clash with West Ham United, made it clear that Lindelof would be an importantly versatile asset at Old Trafford this season. "He is not ready to play tomorrow, so it is not something that's urgent".
"He was very clear, by showing what he did past year, that it was not enough for him", Mourinho was quoted as saying by FourFourTwo.
Jose Mourinho hoping to continue second-season success record with Manchester United
"If the remaining 25 percent don't arrive I will not moan, just go with everything I have to try to win every match we play". My hard work to motivate people to play in the Europa League with ambition and responsibility was hard.
The former Sweden striker was United's top scorer last season, hitting 28 goals as they won the Europa League, the League Cup and the Community Shield.
"Between the players we have lost and the players we have got, I think we are in a similar situation, but with more experience of working together and a much better pre-season".
"He thinks he can do more and wants more at the highest level".
Mourinho still speaks of free agent Ibrahimovic as part of the group, saying he is injured for the start of the season along with other "important players" like Luke Shaw, Ashley Young and Marcos Rojo.
"But we are involved in four competitions and step by step, match after match we are going to fight".